Percentage

ICSE Class 6 Mathematics · Solutions for Class 6 RS Aggarwal ICSE Foundation Mathematics · 112 solved questions

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1(i)Exercise 10(A)

Express the following as a fraction in its lowest terms:

8%

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To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$ and reduce the fraction to its lowest terms.

⇒ 8%

$$\begin{aligned}\Rightarrow 8 \times \frac{1}{100}\\[1em] \Rightarrow \frac{8}{100}\\[1em] \Rightarrow \frac{2}{25}\end{aligned}$$

Hence, 8% = $\mathbf{\frac{2}{25}}$.

1(ii)Exercise 10(A)

Express the following as a fraction in its lowest terms:

36%

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To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$ and reduce the fraction to its lowest terms.

⇒ 36%

$$\begin{aligned}\Rightarrow 36 \times \frac{1}{100}\\[1em] \Rightarrow \frac{36}{100}\\[1em] \Rightarrow \frac{9}{25}\end{aligned}$$

Hence, 36% = $\mathbf{\frac{9}{25}}$.

1(iii)Exercise 10(A)

Express the following as a fraction in its lowest terms:

125%

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To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$ and reduce the fraction to its lowest terms.

⇒ 125%

$$\begin{aligned}\Rightarrow 125 \times \frac{1}{100}\\[1em] \Rightarrow \frac{125}{100}\\[1em] \Rightarrow \frac{5}{4}\end{aligned}$$

Hence, 125% = $\mathbf{\frac{5}{4}}$.

1(iv)Exercise 10(A)

Express the following as a fraction in its lowest terms:

$12\frac{1}{2}$%

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⇒ $12\frac{1}{2}$% = $\frac{25}{2}$%

To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$ and reduce the fraction to its lowest terms.

$$\begin{aligned}\Rightarrow \frac{25}{2} \times \frac{1}{100}\\[1em] \Rightarrow \frac{25}{200}\\[1em] \Rightarrow \frac{1}{8}\end{aligned}$$

Hence, $\mathbf{12\frac{1}{2}}$% = $\mathbf{\frac{1}{8}}$.

1(v)Exercise 10(A)

Express the following as a fraction in its lowest terms:

$26\frac{2}{3}$%

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⇒ $26\frac{2}{3}$% = $\frac{80}{3}$%

To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$ and reduce the fraction to its lowest terms.

$$\begin{aligned}\Rightarrow \frac{80}{3} \times \frac{1}{100}\\[1em] \Rightarrow \frac{80}{300}\\[1em] \Rightarrow \frac{4}{15}\end{aligned}$$

Hence, $\mathbf{26\frac{2}{3}}$% = $\mathbf{\frac{4}{15}}$.

1(vi)Exercise 10(A)

Express the following as a fraction in its lowest terms:

9.6%

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To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$ and reduce the fraction to its lowest terms.

⇒ 9.6%

$$\begin{aligned}\Rightarrow 9.6 \times \frac{1}{100}\\[1em] \Rightarrow \frac{9.6}{100}\\[1em] \Rightarrow \frac{96}{1000}\\[1em] \Rightarrow \frac{12}{125}\end{aligned}$$

Hence, 9.6% = $\mathbf{\frac{12}{125}}$.

1(vii)Exercise 10(A)

Express the following as a fraction in its lowest terms:

0.36%

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To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$ and reduce the fraction to its lowest terms.

⇒ 0.36%

$$\begin{aligned}\Rightarrow 0.36 \times \frac{1}{100}\\[1em] \Rightarrow \frac{0.36}{100}\\[1em] \Rightarrow \frac{36}{10000}\\[1em] \Rightarrow \frac{9}{2500}\end{aligned}$$

Hence, 0.36% = $\mathbf{\frac{9}{2500}}$.

1(viii)Exercise 10(A)

Express the following as a fraction in its lowest terms:

$\frac{4}{5}$%

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To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$ and reduce the fraction to its lowest terms.

⇒ $\frac{4}{5}$%

$$\begin{aligned}\Rightarrow \frac{4}{5} \times \frac{1}{100}\\[1em] \Rightarrow \frac{4}{500}\\[1em] \Rightarrow \frac{1}{125}\end{aligned}$$

Hence, $\mathbf{\frac{4}{5}}$% = $\mathbf{\frac{1}{125}}$.

2(i)Exercise 10(A)

Express each of the following as a decimal:

43%

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To convert a percentage into a decimal, replace the % sign with $\frac{1}{100}$ and express the fraction as a decimal.

⇒ 43%

$$\begin{aligned}\Rightarrow 43 \times \frac{1}{100}\\[1em] \Rightarrow \frac{43}{100}\\[1em] \Rightarrow 0.43\end{aligned}$$

Hence, 43% = 0.43.

2(ii)Exercise 10(A)

Express each of the following as a decimal:

7%

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To convert a percentage into a decimal, replace the % sign with $\frac{1}{100}$ and express the fraction as a decimal.

⇒ 7%

$$\begin{aligned}\Rightarrow 7 \times \frac{1}{100}\\[1em] \Rightarrow \frac{7}{100}\\[1em] \Rightarrow 0.07\end{aligned}$$

Hence, 7% = 0.07.

2(iii)Exercise 10(A)

Express each of the following as a decimal:

120%

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To convert a percentage into a decimal, replace the % sign with $\frac{1}{100}$ and express the fraction as a decimal.

⇒ 120%

$$\begin{aligned}\Rightarrow 120 \times \frac{1}{100}\\[1em] \Rightarrow \frac{120}{100}\\[1em] \Rightarrow 1.2\end{aligned}$$

Hence, 120% = 1.2.

2(iv)Exercise 10(A)

Express each of the following as a decimal:

3.5%

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To convert a percentage into a decimal, replace the % sign with $\frac{1}{100}$ and express the fraction as a decimal.

⇒ 3.5%

$$\begin{aligned}\Rightarrow 3.5 \times \frac{1}{100}\\[1em] \Rightarrow \frac{3.5}{100}\\[1em] \Rightarrow 0.035\end{aligned}$$

Hence, 3.5% = 0.035.

3(i)Exercise 10(A)

Express each of the following as a ratio:

56%

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To convert a percentage into a ratio, first convert the percentage into a fraction in its lowest terms and then write the fraction as a ratio.

⇒ 56%

$$\begin{aligned}\Rightarrow 56 \times \frac{1}{100}\\[1em] \Rightarrow \frac{56}{100}\\[1em] \Rightarrow \frac{14}{25}\\[1em] \Rightarrow 14 : 25\end{aligned}$$

Hence, 56% = 14 : 25.

3(ii)Exercise 10(A)

Express each of the following as a ratio:

$16\frac{2}{3}$%

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⇒ $16\frac{2}{3}$% = $\frac{50}{3}$%

To convert a percentage into a ratio, first convert the percentage into a fraction in its lowest terms and then write the fraction as a ratio.

$$\begin{aligned}\Rightarrow \frac{50}{3} \times \frac{1}{100}\\[1em] \Rightarrow \frac{50}{300}\\[1em] \Rightarrow \frac{1}{6}\\[1em] \Rightarrow 1 : 6\end{aligned}$$

Hence, $\mathbf{16\frac{2}{3}}$% = 1 : 6.

3(iii)Exercise 10(A)

Express each of the following as a ratio:

6.4%

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To convert a percentage into a ratio, first convert the percentage into a fraction in its lowest terms and then write the fraction as a ratio.

⇒ 6.4%

$$\begin{aligned}\Rightarrow 6.4 \times \frac{1}{100}\\[1em] \Rightarrow \frac{6.4}{100}\\[1em] \Rightarrow \frac{64}{1000}\\[1em] \Rightarrow \frac{8}{125}\\[1em] \Rightarrow 8 : 125\end{aligned}$$

Hence, 6.4% = 8 : 125.

3(iv)Exercise 10(A)

Express each of the following as a ratio:

0.8%

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To convert a percentage into a ratio, first convert the percentage into a fraction in its lowest terms and then write the fraction as a ratio.

⇒ 0.8%

$$\begin{aligned}\Rightarrow 0.8 \times \frac{1}{100}\\[1em] \Rightarrow \frac{0.8}{100}\\[1em] \Rightarrow \frac{8}{1000}\\[1em] \Rightarrow \frac{1}{125}\\[1em] \Rightarrow 1 : 125\end{aligned}$$

Hence, 0.8% = 1 : 125.

4Exercise 10(A)

Express 15% as a (i) fraction (ii) decimal (iii) ratio.

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To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$; the fraction may then be written as a decimal or a ratio, as desired.

(i) As a fraction:

⇒ 15%

$\Rightarrow \frac{15}{100}$

$\Rightarrow \frac{3}{20}$

Hence, 15% as a fraction = $\mathbf{\frac{3}{20}}$.

(ii) As a decimal:

⇒ 15%

$\Rightarrow \frac{15}{100}$

$\Rightarrow 0.15$

Hence, 15% as a decimal = 0.15

(iii) As a ratio:

⇒ 15%

$\Rightarrow \frac{15}{100}$

$\Rightarrow \frac{3}{20}$

⇒ 3 : 20

Hence, 15% as a ratio = 3 : 20.

5Exercise 10(A)

Express 136% as a (i) fraction (ii) decimal (iii) ratio.

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To convert a percentage into a fraction, replace the % sign with $\frac{1}{100}$; the fraction may then be written as a decimal or a ratio, as desired.

(i) As a fraction:

⇒ 136%

$\Rightarrow \frac{136}{100}$

$\Rightarrow \frac{34}{25}$

Hence, 136% as a fraction = $\mathbf{\frac{34}{25}}$.

(ii) As a decimal:

⇒ 136%

$\Rightarrow \frac{136}{100}$

$\Rightarrow \frac{34}{25}$

$\Rightarrow 1.36$

Hence, 136% as a decimal = 1.36

(iii) As a ratio:

⇒ 136%

$\Rightarrow \frac{136}{100}$

$\Rightarrow \frac{34}{25}$

$\Rightarrow 34 : 25$

Hence, 136% as a ratio = 34 : 25.

6(i)Exercise 10(A)

Convert each of the following fractions into a percentage:

$\frac{13}{20}$

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To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow \frac{13}{20}$

$\Rightarrow \left(\frac{13}{20} \times 100\right)$%

$\Rightarrow \frac{1300}{20}$%

$\Rightarrow 65$%

Hence, $\mathbf{\frac{13}{20}}$ = 65%.

6(ii)Exercise 10(A)

Convert each of the following fractions into a percentage:

$\frac{7}{16}$

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To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow \frac{7}{16}$

$\Rightarrow \left(\frac{7}{16} \times 100\right)$%

$\Rightarrow \frac{700}{16}$%

$\Rightarrow \frac{175}{4}$%

$\Rightarrow 43\frac{3}{4}$%

Hence, $\mathbf{\frac{7}{16}}$ = $\mathbf{43\frac{3}{4}}$%.

6(iii)Exercise 10(A)

Convert each of the following fractions into a percentage:

$\frac{5}{12}$

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To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow \frac{5}{12}$

$\Rightarrow \left(\frac{5}{12} \times 100\right)$%

$\Rightarrow \frac{500}{12}$%

$\Rightarrow \frac{125}{3}$%

$\Rightarrow 41\frac{2}{3}$%

Hence, $\mathbf{\frac{5}{12}}$ = $\mathbf{41\frac{2}{3}}$%.

6(iv)Exercise 10(A)

Convert each of the following fractions into a percentage:

$2\frac{3}{4}$

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⇒ $2\frac{3}{4} = \frac{11}{4}$

To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow \left(\frac{11}{4} \times 100\right)$%

$\Rightarrow \frac{1100}{4}$%

$\Rightarrow 275$%

Hence, $\mathbf{2\frac{3}{4}}$ = 275%.

6(v)Exercise 10(A)

Convert each of the following fractions into a percentage:

$1\frac{7}{8}$

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⇒ $1\frac{7}{8} = \frac{15}{8}$

To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow \left(\frac{15}{8} \times 100\right)$%

$\Rightarrow \frac{1500}{8}$%

$\Rightarrow \frac{375}{2}$%

$\Rightarrow 187\frac{1}{2}$%

Hence, $\mathbf{1\frac{7}{8}}$ = $\mathbf{187\frac{1}{2}}$%.

6(vi)Exercise 10(A)

Convert each of the following fractions into a percentage:

$\frac{3}{200}$

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To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow \frac{3}{200}$

$\Rightarrow \left(\frac{3}{200} \times 100\right)$%

$\Rightarrow \frac{300}{200}$%

$\Rightarrow \frac{3}{2}$%

$\Rightarrow 1\frac{1}{2}$%

Hence, $\mathbf{\frac{3}{200}}$ = $\mathbf{1\frac{1}{2}}$%.

6(vii)Exercise 10(A)

Convert each of the following fractions into a percentage:

$\frac{24}{5}$

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To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow \frac{24}{5}$

$\Rightarrow \left(\frac{24}{5} \times 100\right)$%

$\Rightarrow \frac{2400}{5}$%

$\Rightarrow 480$%

Hence, $\mathbf{\frac{24}{5}}$ = 480%.

6(viii)Exercise 10(A)

Convert each of the following fractions into a percentage:

3

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To convert a number into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow 3$

$\Rightarrow (3 \times 100)$%

$\Rightarrow 300$%

Hence, 3 = 300%.

7(i)Exercise 10(A)

Convert each of the following decimals into a percentage:

0.7

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To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 0.7

⇒ (0.7 × 100)%

⇒ 70%

Hence, 0.7 = 70%.

7(ii)Exercise 10(A)

Convert each of the following decimals into a percentage:

0.54

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To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 0.54

⇒ (0.54 × 100)%

⇒ 54%

Hence, 0.54 = 54%.

7(iii)Exercise 10(A)

Convert each of the following decimals into a percentage:

0.06

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To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 0.06

⇒ (0.06 × 100)%

⇒ 6%

Hence, 0.06 = 6%.

7(iv)Exercise 10(A)

Convert each of the following decimals into a percentage:

0.073

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To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 0.073

⇒ (0.073 × 100)%

⇒ 7.3%

Hence, 0.073 = 7.3%.

7(v)Exercise 10(A)

Convert each of the following decimals into a percentage:

2.05

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To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 2.05

⇒ (2.05 × 100)%

⇒ 205%

Hence, 2.05 = 205%.

7(vi)Exercise 10(A)

Convert each of the following decimals into a percentage:

4.3

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To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 4.3

⇒ (4.3 × 100)%

⇒ 430%

Hence, 4.3 = 430%.

7(vii)Exercise 10(A)

Convert each of the following decimals into a percentage:

1.065

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To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 1.065

$\Rightarrow \Big(\frac{1065}{1000} \times 100\Big)$%

$\Rightarrow 106\frac{1}{2}$%

Hence, 1.065 = $\mathbf{106\frac{1}{2}}$%.

7(viii)Exercise 10(A)

Convert each of the following decimals into a percentage:

0.005

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To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 0.005 or $\frac{5}{1000}$

$\Rightarrow \Big(\frac{5}{1000} \times 100 \Big)$%

$\Rightarrow \frac{1}{2}$%

Hence, 0.005 = $\mathbf{\frac{1}{2}}$%.

1(i)Exercise 10(B)

Find the value of:

16% of 175

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 16% of 175

$$\begin{aligned}\Rightarrow \frac{16}{100} \times 175\\[1em] \Rightarrow \frac{2800}{100}\\[1em] \Rightarrow 28\end{aligned}$$

Hence, 16% of 175 = 28.

1(ii)Exercise 10(B)

Find the value of:

140% of 45

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 140% of 45

$$\begin{aligned}\Rightarrow \frac{140}{100} \times 45\\[1em] \Rightarrow \frac{6300}{100}\\[1em] \Rightarrow 63\end{aligned}$$

Hence, 140% of 45 = 63.

1(iii)Exercise 10(B)

Find the value of:

2% of 120

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 2% of 120

$$\begin{aligned}\Rightarrow \frac{2}{100} \times 120\\[1em] \Rightarrow \frac{240}{100}\\[1em] \Rightarrow 2.4\end{aligned}$$

Hence, 2% of 120 = 2.4.

1(iv)Exercise 10(B)

Find the value of:

12.5% of 72

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 12.5% of 72

$$\begin{aligned}\Rightarrow \frac{12.5}{100} \times 72\\[1em] \Rightarrow \frac{900}{100}\\[1em] \Rightarrow 9\end{aligned}$$

Hence, 12.5% of 72 = 9.

1(v)Exercise 10(B)

Find the value of:

14% of 14

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 14% of 14

$$\begin{aligned}\Rightarrow \frac{14}{100} \times 14\\[1em] \Rightarrow \frac{196}{100}\\[1em] \Rightarrow 1.96\end{aligned}$$

Hence, 14% of 14 = 1.96.

1(vi)Exercise 10(B)

Find the value of:

$16\frac{2}{3}$% of 18

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⇒ $16\frac{2}{3}$% = $\frac{50}{3}$%

To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ $\frac{50}{3}$% of 18

$$\begin{aligned}\Rightarrow \frac{50}{3 \times 100} \times 18\\[1em] \Rightarrow \frac{50 \times 18}{300}\\[1em] \Rightarrow \frac{900}{300}\\[1em] \Rightarrow 3\end{aligned}$$

Hence, $\mathbf{16\frac{2}{3}}$% of 18 = 3.

1(vii)Exercise 10(B)

Find the value of:

5% of 12.6

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 5% of 12.6

$$\begin{aligned}\Rightarrow \frac{5}{100} \times 12.6\\[1em] \Rightarrow \frac{63}{100}\\[1em] \Rightarrow 0.63\end{aligned}$$

Hence, 5% of 12.6 = 0.63.

1(viii)Exercise 10(B)

Find the value of:

20% of $\frac{1}{3}$

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 20% of $\frac{1}{3}$

$$\begin{aligned}\Rightarrow \frac{20}{100} \times \frac{1}{3}\\[1em] \Rightarrow \frac{20}{300}\\[1em] \Rightarrow \frac{1}{15}\end{aligned}$$

Hence, 20% of $\mathbf{\frac{1}{3}}$ = $\mathbf{\frac{1}{15}}$.

2(i)Exercise 10(B)

Find the value of:

14% of ₹ 75

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 14% of ₹ 75

$$\begin{aligned}\Rightarrow \frac{14}{100} \times 75\\[1em] \Rightarrow \frac{1050}{100}\\[1em] \Rightarrow ₹\ 10.50\end{aligned}$$

Hence, 14% of ₹ 75 = ₹ 10.50.

2(ii)Exercise 10(B)

Find the value of:

60% of 50 kg

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 60% of 50 kg

$$\begin{aligned}\Rightarrow \frac{60}{100} \times 50\\[1em] \Rightarrow \frac{3000}{100}\\[1em] \Rightarrow 30 \text{ kg}\end{aligned}$$

Hence, 60% of 50 kg = 30 kg.

2(iii)Exercise 10(B)

Find the value of:

8% of 65 cm

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

⇒ 8% of 65 cm

$$\begin{aligned}\Rightarrow \frac{8}{100} \times 65\\[1em] \Rightarrow \frac{520}{100}\\[1em] \Rightarrow 5.2 \text{ cm}\end{aligned}$$

Hence, 8% of 65 cm = 5.2 cm.

2(iv)Exercise 10(B)

Find the value of:

5% of 3 kg

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

We know, 1 kg = 1000 g, so 3 kg = 3000 g.

⇒ 5% of 3000 g

$$\begin{aligned}\Rightarrow \frac{5}{100} \times 3000\\[1em] \Rightarrow \frac{15000}{100}\\[1em] \Rightarrow 150 \text{ g}\end{aligned}$$

Hence, 5% of 3 kg = 150 g.

2(v)Exercise 10(B)

Find the value of:

10% of 1 litre

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

We know, 1 litre = 1000 ml.

⇒ 10% of 1000 ml

$$\begin{aligned}\Rightarrow \frac{10}{100} \times 1000\\[1em] \Rightarrow \frac{10000}{100}\\[1em] \Rightarrow 100 \text{ ml}\end{aligned}$$

Hence, 10% of 1 litre = 100 ml.

2(vi)Exercise 10(B)

Find the value of:

40% of 1 year

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

We know, 1 year = 365 days.

⇒ 40% of 365 days

$$\begin{aligned}\Rightarrow \frac{40}{100} \times 365\\[1em] \Rightarrow \frac{14600}{100}\\[1em] \Rightarrow 146 \text{ days}\end{aligned}$$

Hence, 40% of 1 year = 146 days.

2(vii)Exercise 10(B)

Find the value of:

9% of 1 m

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To find a percentage of a given quantity, change the percentage into a fraction and multiply by the given quantity.

We know, 1 m = 100 cm.

⇒ 9% of 100 cm

$$\begin{aligned}\Rightarrow \frac{9}{100} \times 100\\[1em] \Rightarrow 9 \text{ cm}\end{aligned}$$

Hence, 9% of 1 m = 9 cm.

3(i)Exercise 10(B)

What per cent of 95 is 19?

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Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{19}{95} \times 100\right)$%

= $\frac{1900}{95}$%

= 20%

Hence, 19 is 20% of 95.

3(ii)Exercise 10(B)

What per cent of 40 is 32?

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Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{32}{40} \times 100\right)$%

= $\frac{3200}{40}$%

= 80%

Hence, 32 is 80% of 40.

3(iii)Exercise 10(B)

What per cent of 65 is 117?

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Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{117}{65} \times 100\right)$%

= $\frac{11700}{65}$%

= 180%

Hence, 117 is 180% of 65.

3(iv)Exercise 10(B)

What per cent of 42 is 29.4?

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Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{29.4}{42} \times 100\right)$%

= $\frac{2940}{42}$%

= 70%

Hence, 29.4 is 70% of 42.

4(i)Exercise 10(B)

What per cent is 43 p of ₹ 1?

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While comparing two quantities, they must be of the same kind and in the same units.

We know, ₹ 1 = 100 paise.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{43}{100} \times 100\right)$%

= 43%

Hence, 43 p is 43% of ₹ 1.

4(ii)Exercise 10(B)

What per cent is 16 mm of 1 cm?

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While comparing two quantities, they must be of the same kind and in the same units.

We know, 1 cm = 10 mm.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{16}{10} \times 100\right)$%

= $\frac{1600}{10}$%

= 160%

Hence, 16 mm is 160% of 1 cm.

4(iii)Exercise 10(B)

What per cent is 8 cm of 1 m?

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While comparing two quantities, they must be of the same kind and in the same units.

We know, 1 m = 100 cm.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{8}{100} \times 100\right)$%

= 8%

Hence, 8 cm is 8% of 1 m.

4(iv)Exercise 10(B)

What per cent is 635 m of 1 km?

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While comparing two quantities, they must be of the same kind and in the same units.

We know, 1 km = 1000 m.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{635}{1000} \times 100\right)$%

= $\frac{63500}{1000}$%

= 63.5%

Hence, 635 m is 63.5% of 1 km.

5(i)Exercise 10(B)

What per cent is 27 p of ₹ 1.80?

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While comparing two quantities, they must be of the same kind and in the same units.

We know, ₹ 1 = 100 paise, so ₹ 1.80 = (1.80 × 100) paise = 180 paise.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{27}{180} \times 100\right)$%

= $\frac{2700}{180}$%

= 15%

Hence, 27 p is 15% of ₹ 1.80.

5(ii)Exercise 10(B)

What per cent is 48 cm of 1.5 m?

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While comparing two quantities, they must be of the same kind and in the same units.

We know, 1 m = 100 cm, so 1.5 m = (1.5 × 100) cm = 150 cm.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{48}{150} \times 100\right)$%

= $\frac{4800}{150}$%

= 32%

Hence, 48 cm is 32% of 1.5 m.

5(iii)Exercise 10(B)

What per cent is 175 gm of 2.5 kg?

Show SolutionHide Solution↓

While comparing two quantities, they must be of the same kind and in the same units.

We know, 1 kg = 1000 gm, so 2.5 kg = (2.5 × 1000) gm = 2500 gm.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{175}{2500} \times 100\right)$%

= $\frac{17500}{2500}$%

= 7%

Hence, 175 gm is 7% of 2.5 kg.

5(iv)Exercise 10(B)

What per cent is 2 minutes 24 seconds of 1 hour?

Show SolutionHide Solution↓

While comparing two quantities, they must be of the same kind and in the same units.

2 minutes 24 seconds = (2 × 60 + 24) seconds = (120 + 24) seconds = 144 seconds.

1 hour = (60 × 60) seconds = 3600 seconds.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{144}{3600} \times 100\right)$%

= $\frac{14400}{3600}$%

= 4%

Hence, 2 minutes 24 seconds is 4% of 1 hour.

5(v)Exercise 10(B)

What per cent is 189 m of 1.05 km?

Show SolutionHide Solution↓

While comparing two quantities, they must be of the same kind and in the same units.

We know, 1 km = 1000 m, so 1.05 km = (1.05 × 1000) m = 1050 m.

Required percentage = $\left(\frac{\text{1st quantity}}{\text{2nd quantity}} \times 100\right)$%

= $\left(\frac{189}{1050} \times 100\right)$%

= $\frac{18900}{1050}$%

= 18%

Hence, 189 m is 18% of 1.05 km.

6Exercise 10(B)

What is the number whose 8% is 18?

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Let the required number be x.

8% of x = 18

$$\begin{aligned}\Rightarrow \frac{8}{100} \times x = 18\\[1em] \Rightarrow x = \frac{18 \times 100}{8}\\[1em] \Rightarrow x = \frac{1800}{8}\\[1em] \Rightarrow x = 225\end{aligned}$$

Hence, the required number is 225.

7Exercise 10(B)

What is the number whose 6% is 8.1?

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Let the required number be x.

6% of x = 8.1

$$\begin{aligned}\Rightarrow \frac{6}{100} \times x = 8.1\\[1em] \Rightarrow x = \frac{8.1 \times 100}{6}\\[1em] \Rightarrow x = \frac{810}{6}\\[1em] \Rightarrow x = 135\end{aligned}$$

Hence, the required number is 135.

8Exercise 10(B)

What is the amount whose 12% is ₹ 21?

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Let the required amount be ₹ x.

12% of x = 21

$$\begin{aligned}\Rightarrow \frac{12}{100} \times x = 21\\[1em] \Rightarrow x = \frac{21 \times 100}{12}\\[1em] \Rightarrow x = \frac{2100}{12}\\[1em] \Rightarrow x = 175\end{aligned}$$

Hence, the required amount is ₹ 175.

9Exercise 10(B)

What is the length whose 16% is 36 cm?

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Let the required length be x cm.

16% of x = 36

$$\begin{aligned}\Rightarrow \frac{16}{100} \times x = 36\\[1em] \Rightarrow x = \frac{36 \times 100}{16}\\[1em] \Rightarrow x = \frac{3600}{16}\\[1em] \Rightarrow x = 225\end{aligned}$$

Hence, the required length is 225 cm, i.e., 2.25 m.

10Exercise 10(B)

What is the number whose 12.5% is 3.5?

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Let the required number be x.

12.5% of x = 3.5

$$\begin{aligned}\Rightarrow \frac{12.5}{100} \times x = 3.5\\[1em] \Rightarrow x = \frac{3.5 \times 100}{12.5}\\[1em] \Rightarrow x = \frac{350}{12.5}\\[1em] \Rightarrow x = 28\end{aligned}$$

Hence, the required number is 28.

1Exercise 10(C)

In a class test, the marks were awarded out of 80. Kamal obtained 65% marks. How many marks did he get?

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Maximum marks = 80.

Marks obtained by Kamal = 65% of 80

$$\begin{aligned}= \frac{65}{100} \times 80\\[1em] = \frac{5200}{100}\\[1em] = 52\end{aligned}$$

Hence, Kamal got 52 marks.

2Exercise 10(C)

In an examination, Renu obtained 480 marks out of 750. What percentage of marks did she get?

Show SolutionHide Solution↓

Marks obtained by Renu = 480 and maximum marks = 750.

Percentage of marks obtained = $\left(\frac{480}{750} \times 100\right)$%

$= \frac{48000}{750}$%

= 64%

Hence, Renu got 64% marks.

3Exercise 10(C)

In her annual examination Geeta scored 39 marks out of 60 in English and 51 out of 75 in Hindi. In which subject her performance was better?

Show SolutionHide Solution↓

Percentage of marks in English = $\left(\frac{39}{60} \times 100\right)$%

$= \frac{3900}{60}$%

= 65%

Percentage of marks in Hindi = $\left(\frac{51}{75} \times 100\right)$%

$= \frac{5100}{75}$%

= 68%

Since 68% > 65%, her performance in Hindi was better than in English.

Hence, Geeta's performance was better in Hindi.

4Exercise 10(C)

In an examination, 640 students appeared. Of them, 544 passed and the rest failed. What percentage of the students failed?

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Total number of students = 640.

Number of students who passed = 544.

Number of students who failed = 640 − 544 = 96.

Percentage of students who failed = $\left(\frac{96}{640} \times 100\right)$%

$= \frac{9600}{640}$%

= 15%

Hence, 15% of the students failed.

5Exercise 10(C)

In an examination 1360 students appeared. Of them, 85% passed. How many students failed?

Show SolutionHide Solution↓

Total number of students = 1360.

Percentage of students who passed = 85%.

Percentage of students who failed = (100 − 85)% = 15%.

Number of students who failed = 15% of 1360

$$\begin{aligned}= \frac{15}{100} \times 1360\\[1em] = \frac{20400}{100}\\[1em] = 204\end{aligned}$$

Hence, 204 students failed.

6Exercise 10(C)

In an examination, a student has to secure 48% marks to pass. If Rahul gets 247 marks and fails by 5 marks, what are the maximum marks?

Show SolutionHide Solution↓

Marks obtained by Rahul = 247.

Since Rahul fails by 5 marks,

Pass marks = 247 + 5 = 252.

∴ 48% of maximum marks = 252

$$\begin{aligned}\Rightarrow \frac{48}{100} \times \text{(maximum marks)} = 252\\[1em] \Rightarrow \text{Maximum marks} = \frac{252 \times 100}{48}\\[1em] \Rightarrow \text{Maximum marks} = \frac{25200}{48}\\[1em] \Rightarrow \text{Maximum marks} = 525\end{aligned}$$

Hence, the maximum marks are 525.

7Exercise 10(C)

On a particular day, 96% of the students were present in a school. If the number of absentees on that day was 82, find the total strength of the school.

Show SolutionHide Solution↓

Percentage of students present = 96%.

Percentage of absentees = (100 − 96)% = 4%.

∴ 4% of total strength = 82

$$\begin{aligned}\Rightarrow \frac{4}{100} \times \text{(total strength)} = 82\\[1em] \Rightarrow \text{Total strength} = \frac{82 \times 100}{4}\\[1em] \Rightarrow \text{Total strength} = \frac{8200}{4}\\[1em] \Rightarrow \text{Total strength} = 2050\end{aligned}$$

Hence, the total strength of the school is 2050.

8Exercise 10(C)

The population of a town has increased by 5% in a year. Last year its population was 20320. What is the present population of the town?

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Last year's population = 20320.

Increase in population = 5% of 20320

$$\begin{aligned}= \frac{5}{100} \times 20320\\[1em] = \frac{101600}{100}\\[1em] = 1016\end{aligned}$$

Present population = (last year's population + increase)

= 20320 + 1016

= 21336

Hence, the present population of the town is 21336.

9Exercise 10(C)

The price of a bat was ₹ 650. Now, its price has been increased by 6%. What is the increased price of the bat?

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Original price of the bat = ₹ 650.

Increase in its price = 6% of ₹ 650

$$\begin{aligned}= \frac{6}{100} \times 650\\[1em] = \frac{3900}{100}\\[1em] = ₹\ 39\end{aligned}$$

Increased price = (original price + increase)

= ₹ (650 + 39)

= ₹ 689

Hence, the increased price of the bat is ₹ 689.

10Exercise 10(C)

The price of a cooler during last summer was quoted at ₹ 7250. In off season, the price has been reduced by 12%. What is the reduced price of the cooler?

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Original price of the cooler = ₹ 7250.

Reduction in price = 12% of ₹ 7250

$$\begin{aligned}= \frac{12}{100} \times 7250\\[1em] = \frac{87000}{100}\\[1em] = ₹\ 870\end{aligned}$$

Reduced price = (original price − reduction)

= ₹ (7250 − 870)

= ₹ 6380

Hence, the reduced price of the cooler is ₹ 6380.

11Exercise 10(C)

The value of a car depreciates (decreases) by 10% every year. If the value of the new car is ₹ 225000, what will be its value after one year?

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Value of the new car = ₹ 225000.

Depreciation in one year = 10% of ₹ 225000

$$\begin{aligned}= \frac{10}{100} \times 225000\\[1em] = \frac{2250000}{100}\\[1em] = ₹\ 22500\end{aligned}$$

Value after one year = (original value − depreciation)

= ₹ (225000 − 22500)

= ₹ 202500

Hence, the value of the car after one year will be ₹ 202500.

12Exercise 10(C)

Ashish is 175 cm tall. His sister Annu is 8% shorter than him. What is Annu's height?

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Height of Ashish = 175 cm.

Annu is 8% shorter than Ashish.

Difference in height = 8% of 175 cm

$$\begin{aligned}= \frac{8}{100} \times 175\\[1em] = \frac{1400}{100}\\[1em] = 14 \text{ cm}\end{aligned}$$

Annu's height = (175 − 14) cm = 161 cm

Hence, Annu's height is 161 cm.

13Exercise 10(C)

An alloy consists of copper and zinc. It contains 60% copper and the rest is zinc. Find the quantity of copper and zinc in 425 g of this alloy.

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Percentage of copper in the alloy = 60%.

Percentage of zinc in the alloy = (100 − 60)% = 40%.

Quantity of copper in 425 g of alloy = 60% of 425 g

$$\begin{aligned}= \frac{60}{100} \times 425\\[1em] = \frac{25500}{100}\\[1em] = 255 \text{ g}\end{aligned}$$

Quantity of zinc in 425 g of alloy = 40% of 425 g

$$\begin{aligned}= \frac{40}{100} \times 425\\[1em] = \frac{17000}{100}\\[1em] = 170 \text{ g}\end{aligned}$$

Hence, 425 g of the alloy contains 255 g of copper and 170 g of zinc.

14Exercise 10(C)

A tin contained 25 litres of oil. Due to leakage 2 litres of oil was lost. What percentage of oil is still there in the tin?

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Total oil in the tin = 25 litres.

Oil lost due to leakage = 2 litres.

Oil left in the tin = (25 − 2) litres = 23 litres.

Percentage of oil still there in the tin = $\left(\frac{23}{25} \times 100\right)$%

$= \frac{2300}{25}$%

= 92%

Hence, 92% of the oil is still there in the tin.

15Exercise 10(C)

An election was contested by two candidates A and B. In all there were 25000 voters. 80% of the votes were polled. If A got 60% of the total votes polled, how many votes did B get?

Show SolutionHide Solution↓

Total number of voters = 25000.

Number of votes polled = 80% of 25000

$$\begin{aligned}= \frac{80}{100} \times 25000\\[1em] = \frac{2000000}{100}\\[1em] = 20000\end{aligned}$$

Votes got by A = 60% of the total votes polled = 60% of 20000

$$\begin{aligned}= \frac{60}{100} \times 20000\\[1em] = \frac{1200000}{100}\\[1em] = 12000\end{aligned}$$

Votes got by B = (votes polled − votes got by A)

= 20000 − 12000

= 8000

Hence, B got 8000 votes.

16Exercise 10(C)

Mr Mehta had ₹ 60000. Out of this money, he gave 20% to his daughter, 35% to his son, 30% to his wife and the rest he donated to a Charitable Trust. How much did he donate?

Show SolutionHide Solution↓

Total money with Mr Mehta = ₹ 60000.

Percentage of money given to daughter, son and wife = (20 + 35 + 30)% = 85%.

Percentage of money donated = (100 − 85)% = 15%.

Money donated = 15% of ₹ 60000

$$\begin{aligned}= \frac{15}{100} \times 60000\\[1em] = \frac{900000}{100}\\[1em] = ₹\ 9000\end{aligned}$$

Hence, Mr Mehta donated ₹ 9000 to the Charitable Trust.

11 Mark · Exercise 10(D) - Multiple Choice Questions

What per cent of 850 is 36?

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Required percentage = $\left(\frac{36}{850} \times 100\right)$%

$= \frac{3600}{850}$%

$= \frac{72}{17}$%

$= 4\frac{4}{17}$%

Hence, option 3 is the correct option.

21 Mark · Exercise 10(D) - Multiple Choice Questions

What per cent of 65 is 78?

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Required percentage = $\left(\frac{78}{65} \times 100\right)$%

$= \frac{7800}{65}$%

= 120%

Hence, option 3 is the correct option.

31 Mark · Exercise 10(D) - Multiple Choice Questions

If 15% of x = 9, then x = ?

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15% of x = 9

$$\begin{aligned}\Rightarrow \frac{15}{100} \times x = 9\\[1em] \Rightarrow x = \frac{9 \times 100}{15}\\[1em] \Rightarrow x = \frac{900}{15}\\[1em] \Rightarrow x = 60\end{aligned}$$

Hence, option 4 is the correct option.

41 Mark · Exercise 10(D) - Multiple Choice Questions

$6\frac{2}{3}$% when expressed as a ratio, is:

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⇒ $6\frac{2}{3}$% = $\frac{20}{3}$%

$$\begin{aligned}\Rightarrow \frac{20}{3} \times \frac{1}{100}\\[1em] \Rightarrow \frac{20}{300}\\[1em] \Rightarrow \frac{1}{15}\\[1em] \Rightarrow 1 : 15\end{aligned}$$

Hence, option 3 is the correct option.

51 Mark · Exercise 10(D) - Multiple Choice Questions

$16\frac{2}{3}$% when expressed as a fraction, is:

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⇒ $16\frac{2}{3}$% = $\frac{50}{3}$%

$$\begin{aligned}\Rightarrow \frac{50}{3} \times \frac{1}{100}\\[1em] \Rightarrow \frac{50}{300}\\[1em] \Rightarrow \frac{1}{6}\end{aligned}$$

Hence, option 2 is the correct option.

61 Mark · Exercise 10(D) - Multiple Choice Questions

6.5, when expressed as a percentage, is:

Show SolutionHide Solution↓

To convert a decimal into a percentage, multiply it by 100 and put the % sign.

⇒ 6.5

⇒ (6.5 × 100)%

⇒ 650%

Hence, option 2 is the correct option.

71 Mark · Exercise 10(D) - Multiple Choice Questions

$\frac{3}{5}$, when expressed as a percentage, is:

Show SolutionHide Solution↓

To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\Rightarrow \frac{3}{5}$

$\Rightarrow \left(\frac{3}{5} \times 100\right)$%

$\Rightarrow \frac{300}{5}$%

$\Rightarrow 60$%

Hence, option 1 is the correct option.

81 Mark · Exercise 10(D) - Multiple Choice Questions

What percent is 27 paise of ₹ 1.80?

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We know, ₹ 1 = 100 paise, so ₹ 1.80 = (1.80 × 100) paise = 180 paise.

Required percentage = $\left(\frac{27}{180} \times 100\right)$%

$= \frac{2700}{180}$%

= 15%

Hence, option 2 is the correct option.

91 Mark · Exercise 10(D) - Multiple Choice Questions

What per cent is 48 cm of 1.5 m?

Show SolutionHide Solution↓

We know, 1 m = 100 cm, so 1.5 m = (1.5 × 100) cm = 150 cm.

Required percentage = $\left(\frac{48}{150} \times 100\right)$%

$= \frac{4800}{150}$%

= 32%

Hence, option 1 is the correct option.

101 Mark · Exercise 10(D) - Multiple Choice Questions

What per cent is 175 g of 2.5 kg?

Show SolutionHide Solution↓

We know, 1 kg = 1000 g, so 2.5 kg = (2.5 × 1000) g = 2500 g.

Required percentage = $\left(\frac{175}{2500} \times 100\right)$%

$= \frac{17500}{2500}$%

= 7%

Hence, option 3 is the correct option.

111 Mark · Exercise 10(D) - Multiple Choice Questions

The price of a bicycle is reduced from ₹ 4000 to ₹ 3500. The percentage decrease in the price is:

Show SolutionHide Solution↓

Original price = ₹ 4000 and reduced price = ₹ 3500.

Decrease in price = ₹ (4000 − 3500) = ₹ 500.

Percentage decrease = $\left(\frac{\text{Decrease}}{\text{Original price}} \times 100\right)$%

$= \left(\frac{500}{4000} \times 100\right)$%

$= \frac{50000}{4000}$%

= 12.5%

Hence, option 3 is the correct option.

121 Mark · Exercise 10(D) - Multiple Choice Questions

80% of teachers in a school are females and the number of male teachers is 25. The number of female teachers is:

Show SolutionHide Solution↓

Let the total number of teachers be x.

Percentage of female teachers = 80%.

Percentage of male teachers = (100 − 80)% = 20%.

Then, 20% of x = 25

$$\begin{aligned}\Rightarrow \frac{20}{100} \times x = 25\\[1em] \Rightarrow x = \frac{25 \times 100}{20}\\[1em] \Rightarrow x = 125\end{aligned}$$

Number of female teachers = 80% of 125

$$\begin{aligned}= \frac{80}{100} \times 125\\[1em] = \frac{10000}{100}\\[1em] = 100\end{aligned}$$

Hence, option 2 is the correct option.

131 Mark · Exercise 10(D) - Multiple Choice Questions

A mixture of milk and water contains 8 parts of milk and 2 parts of water. The percentage of milk in the mixture is:

Show SolutionHide Solution↓

Total parts in the mixture = 8 + 2 = 10.

Out of 10 parts, milk = 8 parts.

Percentage of milk in the mixture = $\left(\frac{8}{10} \times 100\right)$%

$= \frac{800}{10}$%

= 80%

Hence, option 4 is the correct option.

141 Mark · Exercise 10(D) - Multiple Choice Questions

An alloy contains 35% zinc, 20% copper and rest nickel. In 1.5 kg of alloy, the quantity of nickel is:

Show SolutionHide Solution↓

Percentage of zinc and copper = (35 + 20)% = 55%.

Percentage of nickel = (100 − 55)% = 45%.

We know, 1 kg = 1000 g, so 1.5 kg = 1500 g.

Quantity of nickel in 1.5 kg of alloy = 45% of 1500 g

$$\begin{aligned}= \frac{45}{100} \times 1500\\[1em] = \frac{67500}{100}\\[1em] = 675 \text{ g}\end{aligned}$$

Hence, option 3 is the correct option.

1Exercise 10(D) - Mental Maths

Fill in the blanks:

(i) 25% of ................. = 45

(ii) 15% of ₹ ................. = ₹ 9

(iii) 8% of ................. kg = 480 g

(iv) 2% of ................. km = 100 m

(v) 9% of ................. m = 18 cm

Show SolutionHide Solution↓

(i) Let 25% of x = 45.

$$\begin{aligned}\Rightarrow \frac{25}{100} \times x = 45\\[1em] \Rightarrow x = \frac{45 \times 100}{25}\\[1em] \Rightarrow x = 180\end{aligned}$$

Hence, 25% of 180 = 45.

(ii) Let 15% of ₹ x = ₹ 9.

$$\begin{aligned}\Rightarrow \frac{15}{100} \times x = 9\\[1em] \Rightarrow x = \frac{9 \times 100}{15}\\[1em] \Rightarrow x = 60\end{aligned}$$

Hence, 15% of ₹ 60 = ₹ 9.

(iii) Let 8% of x kg = 480 g.

We know, 480 g = $\frac{480}{1000}$ kg = 0.48 kg.

$$\begin{aligned}\Rightarrow \frac{8}{100} \times x = 0.48\\[1em] \Rightarrow x = \frac{0.48 \times 100}{8}\\[1em] \Rightarrow x = 6\end{aligned}$$

Hence, 8% of 6 kg = 480 g.

(iv) Let 2% of x km = 100 m.

We know, 100 m = $\frac{100}{1000}$ km = 0.1 km.

$$\begin{aligned}\Rightarrow \frac{2}{100} \times x = 0.1\\[1em] \Rightarrow x = \frac{0.1 \times 100}{2}\\[1em] \Rightarrow x = 5\end{aligned}$$

Hence, 2% of 5 km = 100 m.

(v) Let 9% of x m = 18 cm.

We know, 18 cm = $\frac{18}{100}$ m = 0.18 m.

$$\begin{aligned}\Rightarrow \frac{9}{100} \times x = 0.18\\[1em] \Rightarrow x = \frac{0.18 \times 100}{9}\\[1em] \Rightarrow x = 2\end{aligned}$$

Hence, 9% of 2 m = 18 cm.

2Exercise 10(D) - Mental Maths

Fill in the blanks:

(i) 175 g is ................. % of 2.5 kg.

(ii) $\frac{3}{5}$ expressed as percentage is ................. %.

(iii) If 6% of x is 0.21, then x = ................. .

(iv) Renu obtained 57 marks out of 150. She got ................. % marks.

(v) When ₹ 80 is increased by 15%, we get ₹ ................. .

(vi) ₹ 120 decreased by 15% = ₹ ................. .

Show SolutionHide Solution↓

(i) We know, 2.5 kg = 2500 g.

Required percentage = $\left(\frac{175}{2500} \times 100\right)$%

= $\frac{17500}{2500}$%

= 7%

Hence, 175 g is 7% of 2.5 kg.

(ii) To convert a fraction into a percentage, multiply it by 100 and put the % sign.

$\frac{3}{5} = \left(\frac{3}{5} \times 100\right)$%

= $\frac{300}{5}$%

= 60%

Hence, $\mathbf{\frac{3}{5}}$ expressed as percentage is 60%.

(iii) 6% of x = 0.21

$$\begin{aligned}\Rightarrow \frac{6}{100} \times x = 0.21\\[1em] \Rightarrow x = \frac{0.21 \times 100}{6}\\[1em] \Rightarrow x = \frac{21}{6}\\[1em] \Rightarrow x = 3.5\end{aligned}$$

Hence, if 6% of x is 0.21, then x = 3.5.

(iv) Percentage of marks = $\left(\frac{57}{150} \times 100\right)$%

= $\frac{5700}{150}$%

= 38%

Hence, Renu got 38% marks.

(v) Increase = 15% of ₹ 80

= $\frac{15}{100} \times 80$

= ₹ 12.

Increased amount = ₹ (80 + 12) = ₹ 92.

Hence, when ₹ 80 is increased by 15%, we get ₹ 92.

(vi) Decrease = 15% of ₹ 120

= $\frac{15}{100} \times 120$

= ₹ 18.

Decreased amount = ₹ (120 − 18) = ₹ 102.

Hence, ₹ 120 decreased by 15% = ₹ 102.

3Exercise 10(D) - Mental Maths

Write (T) for true and (F) for false for each of the following statements:

(i) 0.023 = 2.3%

(ii) Per cent means out of 100

(iii) 5% of 1 cm = 5 mm

(iv) 123% = 12.3

(v) 8% = 0.8

Show SolutionHide Solution↓

(i) 0.023 = (0.023 × 100)% = 2.3%.

Hence, the statement is true (T).

(ii) By definition, per cent means per hundred or out of 100.

Hence, the statement is true (T).

(iii) We know that,

1 cm = 10 mm

5% of 1 cm = $\frac{5}{100} \times 10$ mm = 0.5 mm ≠ 5 mm.

Hence, the statement is false (F).

(iv) 123% = $\frac{123}{100}$ = 1.23 ≠ 12.3.

Hence, the statement is false (F).

(v) 8% = $\frac{8}{100}$ = 0.08 ≠ 0.8.

Hence, the statement is false (F).

1Exercise 10(D) - Case Study Based Questions

A teacher asked her students about their preferences for a school excursion. 45% students wanted to go to the amusement park, 15% to a zoo, 10% to a museum and the rest had no preference.

Show SolutionHide Solution↓

1. Let the total number of students be x.

45% of x = 36

$$\begin{aligned}\Rightarrow \frac{45}{100} \times x = 36\\[1em] \Rightarrow x = \frac{36 \times 100}{45}\\[1em] \Rightarrow x = \frac{3600}{45}\\[1em] \Rightarrow x = 80\end{aligned}$$

Hence, option (b) is the correct option.

2. Total number of students = 80.

Number of students who preferred going to the zoo = 15% of 80.

$$\begin{aligned}= \frac{15}{100} \times 80\\[1em] = \frac{1200}{100}\\[1em] = 12\end{aligned}$$

Hence, option (c) is the correct option.

3. Total number of students = 80.

Number of students who preferred going to the museum = 10% of 80

$$\begin{aligned}= \frac{10}{100} \times 80\\[1em] = \frac{800}{100}\\[1em] = 8\end{aligned}$$

Hence, option (a) is the correct option.

4. Percentage of students with no preference = [100 − (45 + 15 + 10)]% = (100 − 70)% = 30%.

Percentage of students who wanted to go to the amusement park = 45%.

Required ratio = 30% : 45%

$= \frac{30}{45}$

$= \frac{2}{3}$

= 2 : 3

Hence, option (c) is the correct option.

2Exercise 10(D) - Case Study Based Questions

In his end-term examination, Rohan scored 54 out of 75 in English, 51 out of 75 in Hindi, 64 out of 80 in Mathematics and 60 out of 80 in Science.

Show SolutionHide Solution↓

1. Percentage of marks in English = $\left(\frac{54}{75} \times 100\right)$%

$= \frac{5400}{75}$%

= 72%

Hence, option (a) is the correct option.

2. Percentage of marks in Science = $\left(\frac{60}{80} \times 100\right)$%

$= \frac{6000}{80}$%

= 75%

Hence, option (c) is the correct option.

3. Percentage of marks in English = $\left(\frac{54}{75} \times 100\right)$% = 72%

Percentage of marks in Hindi = $\left(\frac{51}{75} \times 100\right)$% = 68%

Percentage of marks in Mathematics = $\left(\frac{64}{80} \times 100\right)$% = 80%

Percentage of marks in Science = $\left(\frac{60}{80} \times 100\right)$% = 75%

Since 80% is the highest percentage, Rohan performed the best in Mathematics.

Hence, option (d) is the correct option.

4. Percentage of marks in English = 72%, Hindi = 68%, Mathematics = 80% and Science = 75%.

Since 68% is the lowest percentage, Rohan performed the worst in Hindi.

Hence, option (b) is the correct option.

1Exercise 10(D) - Assertion–Reason Questions

Assertion (A): When an improper fraction is converted into a percentage, then the answer is always greater than 100.

Reason (R): In any question, % sign can be replaced with $\frac{1}{100}$.

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An improper fraction is always greater than 1. On multiplying it by 100, the result is always greater than 100.

For example, $\frac{5}{4} = \left(\frac{5}{4} \times 100\right)$% = 125% > 100%.

So, Assertion (A) is true.

We know that % means per hundred, so in any question the % sign can be replaced with $\frac{1}{100}$. So, Reason (R) is true.

However, the Assertion follows from the fact that a fraction or decimal is converted into a percentage by multiplying it by 100, and not from replacing the % sign with $\frac{1}{100}$. So, Reason (R) is not the correct explanation of Assertion (A).

Hence, option 2 is the correct option.

2Exercise 10(D) - Assertion–Reason Questions

Assertion (A): Out of 600 students of a school, 150 go for a picnic. The percentage of students that did not go for the picnic is 75.

Reason (R): To find the percentage of a given quantity, convert the given percentage into a fraction and divide by the given quantity.

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Total number of students = 600.

Number of students who went for the picnic = 150.

Number of students who did not go for the picnic = 600 − 150 = 450.

Percentage of students who did not go for the picnic = $\left(\frac{450}{600} \times 100\right)$%

$= \frac{45000}{600}$%

= 75%

So, Assertion (A) is true.

To find the percentage of a given quantity, we convert the given percentage into a fraction and multiply it by the given quantity, and not divide it by the given quantity. So, Reason (R) is false.

Assertion (A) is true and Reason (R) is false.

Hence, option 3 is the correct option.

1Exercise 10(D) - Competency Focused Questions

A product's price increases from ₹ 89.50 to ₹ 99.45. By what percentage (to 2 decimal places) did the price increase?

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Original price = ₹ 89.50 and new price = ₹ 99.45.

Increase in price = ₹ (99.45 − 89.50) = ₹ 9.95.

Percentage increase = $\left(\frac{\text{Increase}}{\text{Original price}} \times 100\right)$%

$= \left(\frac{9.95}{89.50} \times 100\right)$%

$= \frac{995}{89.5}$%

= 11.12% (to 2 decimal places)

Hence, option 3 is the correct option.

2Exercise 10(D) - Competency Focused Questions

A school survey shows the favourite subjects of students:

(i) 40% like Math

(ii) 30% like Science

(iii) 20% like English

(iv) 10% like Social Science

If 300 students participated in the survey, how many students like Math and Science combined?

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Percentage of students who like Math and Science combined = (40 + 30)% = 70%.

Number of students who like Math and Science combined = 70% of 300

$$\begin{aligned}= \frac{70}{100} \times 300\\[1em] = \frac{21000}{100}\\[1em] = 210\end{aligned}$$

Hence, option 3 is the correct option.

3Exercise 10(D) - Competency Focused Questions

Two numbers are in the ratio 3 : 5. If 40% of the smaller number is 24, then 60% of the larger number is:

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Let the two numbers be 3x and 5x. Then, the smaller number = 3x and the larger number = 5x.

40% of the smaller number = 24

$$\begin{aligned}\Rightarrow \frac{40}{100} \times 3x = 24\\[1em] \Rightarrow \frac{120x}{100} = 24\\[1em] \Rightarrow x = \frac{24 \times 100}{120}\\[1em] \Rightarrow x = 20\end{aligned}$$

So, the larger number = 5x = 5 × 20 = 100.

60% of the larger number = 60% of 100

$= \frac{60}{100} \times 100$

= 60

Hence, option 4 is the correct option.

4Exercise 10(D) - Competency Focused Questions

A rectangular garden is divided into four sections, and the percentages of the garden used for each purpose are:

Flowers: 30%, Vegetables: 25%, Grass: 35%, Trees: 10%

If the total area of the garden is 800 m2, what is the area used for vegetables and flowers?

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Percentage of the garden used for vegetables and flowers = (25 + 30)% = 55%.

Area used for vegetables and flowers = 55% of 800 m2

$$\begin{aligned}= \frac{55}{100} \times 800\\[1em] = \frac{44000}{100}\\[1em] = 440 \text{ m}^2\end{aligned}$$

Hence, option 1 is the correct option.

5Exercise 10(D) - Competency Focused Questions

A farmer's field produces wheat. 20% of the harvest is used for personal consumption, and 40% is sold to the market. The remaining 60 tonnes are stored. What was the total harvest of wheat?

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Percentage of harvest used for personal consumption and sold to the market = (20 + 40)% = 60%.

Percentage of harvest stored = (100 − 60)% = 40%.

Let the total harvest be x tonnes.

40% of x = 60

$$\begin{aligned}\Rightarrow \frac{40}{100} \times x = 60\\[1em] \Rightarrow x = \frac{60 \times 100}{40}\\[1em] \Rightarrow x = 150\end{aligned}$$

Hence, option 3 is the correct option.

6Exercise 10(D) - Competency Focused Questions

75% of a number when added to 75 is equal to the number. The number is:

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Let the required number be x.

75% of x + 75 = x

$$\begin{aligned}\Rightarrow \frac{75}{100} \times x + 75 = x\\[1em] \Rightarrow \frac{3x}{4} + 75 = x\\[1em] \Rightarrow x - \frac{3x}{4} = 75\\[1em] \Rightarrow \frac{x}{4} = 75\\[1em] \Rightarrow x = 75 \times 4\\[1em] \Rightarrow x = 300\end{aligned}$$

Hence, option 3 is the correct option.

7Exercise 10(D) - Competency Focused Questions

Ajay, Kapil and Varun are three friends studying in the same class. In a class test in Maths, Ajay got 40 out of 50, and Kapil got 36. The average score of the friends was 82%. In that test Varun scored:

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The test was out of 50 marks.

Average score of the three friends = 82% of 50

$$\begin{aligned}= \frac{82}{100} \times 50\\[1em] = \frac{4100}{100}\\[1em] = 41 \text{ marks}\end{aligned}$$

Total marks of the three friends = 41 × 3 = 123.

Marks of Ajay and Kapil = 40 + 36 = 76.

Marks scored by Varun = 123 − 76 = 47.

Hence, option 3 is the correct option.

8Exercise 10(D) - Competency Focused Questions

Two alloys A and B contain gold and copper in the ratio 3 : 2 and 4 : 3 respectively. A 10 kg mixture is prepared by mixing equal quantities of A and B. What percentage of gold is present in the final mixture?

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Since equal quantities of A and B are mixed to prepare 10 kg of mixture,

Quantity of alloy A = quantity of alloy B = 5 kg.

In alloy A, gold : copper = 3 : 2, so sum of ratio terms = 3 + 2 = 5.

Gold in 5 kg of alloy A = $\frac{3}{5} \times 5$ = 3 kg.

In alloy B, gold : copper = 4 : 3, so sum of ratio terms = 4 + 3 = 7.

Gold in 5 kg of alloy B = $\frac{4}{7} \times 5 = \frac{20}{7}$ kg.

Total gold in the mixture = $3 + \frac{20}{7} = \frac{21 + 20}{7} = \frac{41}{7}$ kg.

Percentage of gold in the final mixture = $\left(\frac{41}{7 \times 10} \times 100\right)$%

$= \frac{4100}{70}$%

$= \frac{410}{7}$%

= 58.57% (approx.)

Hence, option 2 is the correct option.

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