Simple Equations

ICSE Class 6 Mathematics · Solutions for Class 6 RS Aggarwal ICSE Foundation Mathematics · 46 solved questions

Exercise
Marks
1(i)Exercise 13(A)

Solve:

$x - 4 = 8$

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Solving,

$$\begin{aligned}\Rightarrow x - 4 = 8 \\[1em] \text{ [Adding 4 on each side] } \\[1em] \Rightarrow x - 4 + 4 = 8 + 4 \\[1em] \Rightarrow x + 0 = 12 \\[1em] \Rightarrow x = 12\end{aligned}$$

Hence, $\bm{x = 12}$.

1(ii)Exercise 13(A)

Solve:

$x + 7 = 2$

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Solving,

$$\begin{aligned}\Rightarrow x + 7 = 2 \\[1em] \text{ [Subtracting 7 from each side] } \\[1em] \Rightarrow x + 7 - 7 = 2 - 7 \\[1em] \Rightarrow x + 0 = -5 \\[1em] \Rightarrow x = -5\end{aligned}$$

Hence, $\bm{x = -5}$.

1(iii)Exercise 13(A)

Solve:

$x - 6 = -3$

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Solving,

$$\begin{aligned}\Rightarrow x - 6 = -3 \\[1em] \text{ [Adding 6 on each side] } \\[1em] \Rightarrow x - 6 + 6 = -3 + 6 \\[1em] \Rightarrow x + 0 = 3 \\[1em] \Rightarrow x = 3\end{aligned}$$

Hence, $\bm{x = 3}$.

1(iv)Exercise 13(A)

Solve:

$y + 2 = -6$

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Solving,

$$\begin{aligned}\Rightarrow y + 2 = -6 \\[1em] \text{ [Subtracting 2 from each side] } \\[1em] \Rightarrow y + 2 - 2 = -6 - 2 \\[1em] \Rightarrow y + 0 = -8 \\[1em] \Rightarrow y = -8\end{aligned}$$

Hence, $\bm{y = -8}$.

1(v)Exercise 13(A)

Solve:

$x + 3 = -1$

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Solving,

$$\begin{aligned}\Rightarrow x + 3 = -1 \\[1em] \text{ [Subtracting 3 from each side] } \\[1em] \Rightarrow x + 3 - 3 = -1 - 3 \\[1em] \Rightarrow x + 0 = -4 \\[1em] \Rightarrow x = -4\end{aligned}$$

Hence, $\bm{x = -4}$.

1(vi)Exercise 13(A)

Solve:

$z - 5 = -8$

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Solving,

$$\begin{aligned}\Rightarrow z - 5 = -8 \\[1em] \text{ [Adding 5 on each side] } \\[1em] \Rightarrow z - 5 + 5 = -8 + 5 \\[1em] \Rightarrow z + 0 = -3 \\[1em] \Rightarrow z = -3\end{aligned}$$

Hence, $\bm{z = -3}$.

2(i)Exercise 13(A)

Solve:

$\frac{x}{3} = 6$

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Solving,

$$\begin{aligned}\Rightarrow \frac{x}{3} = 6 \\[1em] \text{ [Multiplying each side by 3] } \\[1em] \Rightarrow \frac{x}{3} \times 3 = 6 \times 3 \\[1em] \Rightarrow x = 18\end{aligned}$$

Hence, $\bm{x = 18}$.

2(ii)Exercise 13(A)

Solve:

$\frac{y}{2} = -4$

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Solving,

$$\begin{aligned}\Rightarrow \frac{y}{2} = -4 \\[1em] \text{ [Multiplying each side by 2] } \\[1em] \Rightarrow \frac{y}{2} \times 2 = -4 \times 2 \\[1em] \Rightarrow y = -8\end{aligned}$$

Hence, $\bm{y = -8}$.

2(iii)Exercise 13(A)

Solve:

$\frac{2x}{4} = 3$

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Solving,

$$\begin{aligned}\Rightarrow \frac{2x}{4} = 3 \\[1em] \Rightarrow \frac{x}{2} = 3 \\[1em] \text{ [Multiplying each side by 2] } \\[1em] \Rightarrow \frac{x}{2} \times 2 = 3 \times 2 \\[1em] \Rightarrow x = 6\end{aligned}$$

Hence, $\bm{x = 6}$.

3(i)Exercise 13(A)

Solve:

$2x = 10$

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Solving,

$$\begin{aligned}\Rightarrow 2x = 10 \\[1em] \text{ [Dividing each side by 2] } \\[1em] \Rightarrow \frac{2x}{2} = \frac{10}{2} \\[1em] \Rightarrow x = 5\end{aligned}$$

Hence, $\bm{x = 5}$.

3(ii)Exercise 13(A)

Solve:

$3y = -12$

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Solving,

$$\begin{aligned}\Rightarrow 3y = -12 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow \frac{3y}{3} = \frac{-12}{3} \\[1em] \Rightarrow y = -4\end{aligned}$$

Hence, $\bm{y = -4}$.

3(iii)Exercise 13(A)

Solve:

$2x - 3 = 7$

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Solving,

$$\begin{aligned}\Rightarrow 2x - 3 = 7 \\[1em] \text{ [Adding 3 on each side] } \\[1em] \Rightarrow 2x - 3 + 3 = 7 + 3 \\[1em] \Rightarrow 2x = 10 \\[1em] \text{ [Dividing each side by 2] } \\[1em] \Rightarrow \frac{2x}{2} = \frac{10}{2} \\[1em] \Rightarrow x = 5\end{aligned}$$

Hence, $\bm{x = 5}$.

3(iv)Exercise 13(A)

Solve:

$3x - 5 = 4$

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Solving,

$$\begin{aligned}\Rightarrow 3x - 5 = 4 \\[1em] \text{ [Adding 5 on each side] } \\[1em] \Rightarrow 3x - 5 + 5 = 4 + 5 \\[1em] \Rightarrow 3x = 9 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow \frac{3x}{3} = \frac{9}{3} \\[1em] \Rightarrow x = 3\end{aligned}$$

Hence, $\bm{x = 3}$.

3(v)Exercise 13(A)

Solve:

$4x - 1 = 7$

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Solving,

$$\begin{aligned}\Rightarrow 4x - 1 = 7 \\[1em] \text{ [Adding 1 on each side] } \\[1em] \Rightarrow 4x - 1 + 1 = 7 + 1 \\[1em] \Rightarrow 4x = 8 \\[1em] \text{ [Dividing each side by 4] } \\[1em] \Rightarrow \frac{4x}{4} = \frac{8}{4} \\[1em] \Rightarrow x = 2\end{aligned}$$

Hence, $\bm{x = 2}$.

3(vi)Exercise 13(A)

Solve:

$5z - 3 = 2$

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Solving,

$$\begin{aligned}\Rightarrow 5z - 3 = 2 \\[1em] \text{ [Adding 3 on each side] } \\[1em] \Rightarrow 5z - 3 + 3 = 2 + 3 \\[1em] \Rightarrow 5z = 5 \\[1em] \text{ [Dividing each side by 5] } \\[1em] \Rightarrow \frac{5z}{5} = \frac{5}{5} \\[1em] \Rightarrow z = 1\end{aligned}$$

Hence, $\bm{z = 1}$.

4(i)Exercise 13(A)

Solve:

$2x - 3 = -5$

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Solving,

$$\begin{aligned}\Rightarrow 2x - 3 = -5 \\[1em] \text{ [Adding 3 on each side] } \\[1em] \Rightarrow 2x - 3 + 3 = -5 + 3 \\[1em] \Rightarrow 2x = -2 \\[1em] \text{ [Dividing each side by 2] } \\[1em] \Rightarrow \frac{2x}{2} = \frac{-2}{2} \\[1em] \Rightarrow x = -1\end{aligned}$$

Hence, $\bm{x = -1}$.

4(ii)Exercise 13(A)

Solve:

$4y + 5 = -3$

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Solving,

$$\begin{aligned}\Rightarrow 4y + 5 = -3 \\[1em] \text{ [Subtracting 5 from each side] } \\[1em] \Rightarrow 4y + 5 - 5 = -3 - 5 \\[1em] \Rightarrow 4y = -8 \\[1em] \text{ [Dividing each side by 4] } \\[1em] \Rightarrow \frac{4y}{4} = \frac{-8}{4} \\[1em] \Rightarrow y = -2\end{aligned}$$

Hence, $\bm{y = -2}$.

4(iii)Exercise 13(A)

Solve:

$6z - 8 = 1$

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Solving,

$$\begin{aligned}\Rightarrow 6z - 8 = 1 \\[1em] \text{ [Adding 8 on each side] } \\[1em] \Rightarrow 6z - 8 + 8 = 1 + 8 \\[1em] \Rightarrow 6z = 9 \\[1em] \text{ [Dividing each side by 6] } \\[1em] \Rightarrow \frac{6z}{6} = \frac{9}{6} \\[1em] \Rightarrow z = \frac{3}{2}\end{aligned}$$

Hence, $\bm{z = \frac{3}{2}}$.

1Exercise 13(B)

Solve:

$5x + 4 = 19$

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Solving,

$$\begin{aligned}\Rightarrow 5x + 4 = 19 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 5x = 19 - 4 \\[1em] \Rightarrow 5x = 15 \\[1em] \text{ [Dividing each side by 5] } \\[1em] \Rightarrow x = \frac{15}{5} \\[1em] \Rightarrow x = 3.\end{aligned}$$

Hence, $\bm{x = 3}$.

2Exercise 13(B)

Solve:

$3x - 8 = 10$

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Solving,

$$\begin{aligned}\Rightarrow 3x - 8 = 10 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 3x = 10 + 8 \\[1em] \Rightarrow 3x = 18 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow x = \frac{18}{3} \\[1em] \Rightarrow x = 6.\end{aligned}$$

Hence, $\bm{x = 6}$.

3Exercise 13(B)

Solve:

$5 - 2y = 9$

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Solving,

$$\begin{aligned}\Rightarrow 5 - 2y = 9 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow -2y = 9 - 5 \\[1em] \Rightarrow -2y = 4 \\[1em] \text{ [Dividing each side by −2] } \\[1em] \Rightarrow y = \frac{4}{-2} \\[1em] \Rightarrow y = -2.\end{aligned}$$

Hence, $\bm{y = -2}$.

4Exercise 13(B)

Solve:

$-6 + 3x = -5$

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Solving,

$$\begin{aligned}\Rightarrow -6 + 3x = -5 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 3x = -5 + 6 \\[1em] \Rightarrow 3x = 1 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow x = \frac{1}{3}.\end{aligned}$$

Hence, $\bm{x = \frac{1}{3}}$.

5Exercise 13(B)

Solve:

$2x + 12 = 3 - x$

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Solving,

$$\begin{aligned}\Rightarrow 2x + 12 = 3 - x \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 2x + x = 3 - 12 \\[1em] \Rightarrow 3x = -9 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow x = \frac{-9}{3} \\[1em] \Rightarrow x = -3.\end{aligned}$$

Hence, $\bm{x = -3}$.

6Exercise 13(B)

Solve:

$2 - 5y = 2y - 5$

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Solving,

$$\begin{aligned}\Rightarrow 2 - 5y = 2y - 5 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow -5y - 2y = -5 - 2 \\[1em] \Rightarrow -7y = -7 \\[1em] \text{ [Dividing each side by −7] } \\[1em] \Rightarrow y = \frac{-7}{-7} \\[1em] \Rightarrow y = 1.\end{aligned}$$

Hence, $\bm{y = 1}$.

7Exercise 13(B)

Solve:

$\frac{x}{5} + 5 = 2$

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Solving,

$$\begin{aligned}\Rightarrow \frac{x}{5} + 5 = 2 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{x}{5} = 2 - 5 \\[1em] \Rightarrow \frac{x}{5} = -3 \\[1em] \text{ [Multiplying each side by 5] } \\[1em] \Rightarrow x = -3 \times 5 \\[1em] \Rightarrow x = -15.\end{aligned}$$

Hence, $\bm{x = -15}$.

8Exercise 13(B)

Solve:

$\frac{4x}{3} + 3 = x - 2$

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Solving,

$$\begin{aligned}\Rightarrow \frac{4x}{3} + 3 = x - 2 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{4x}{3} - x = -2 - 3 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{4x - 3x}{3} = -5 \\[1em] \Rightarrow \frac{x}{3} = -5 \\[1em] \text{ [Multiplying each side by 3] } \\[1em] \Rightarrow x = -5 \times 3 \\[1em] \Rightarrow x = -15.\end{aligned}$$

Hence, $\bm{x = -15}$.

9Exercise 13(B)

Solve:

$\frac{3x + 2}{5} = 4$

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Solving,

$$\begin{aligned}\Rightarrow \frac{3x + 2}{5} = 4 \\[1em] \text{ [Multiplying each side by 5] } \\[1em] \Rightarrow 3x + 2 = 4 \times 5 \\[1em] \Rightarrow 3x + 2 = 20 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 3x = 20 - 2 \\[1em] \Rightarrow 3x = 18 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow x = \frac{18}{3} \\[1em] \Rightarrow x = 6.\end{aligned}$$

Hence, $\bm{x = 6}$.

10Exercise 13(B)

Solve:

$\frac{x}{2} - 6 = \frac{x}{3} - 5$

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Solving,

$$\begin{aligned}\Rightarrow \frac{x}{2} - 6 = \frac{x}{3} - 5 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{x}{2} - \frac{x}{3} = -5 + 6 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{3x - 2x}{6} = 1 \\[1em] \Rightarrow \frac{x}{6} = 1 \\[1em] \text{ [Multiplying each side by 6] } \\[1em] \Rightarrow x = 6.\end{aligned}$$

Hence, $\bm{x = 6}$.

11Exercise 13(B)

Solve:

$\frac{2y}{3} - 8 = 2 - y$

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Solving,

$$\begin{aligned}\Rightarrow \frac{2y}{3} - 8 = 2 - y \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{2y}{3} + y = 2 + 8 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{2y + 3y}{3} = 10 \\[1em] \Rightarrow \frac{5y}{3} = 10 \\[1em] \text{ [Multiplying each side by 3] } \\[1em] \Rightarrow 5y = 30 \\[1em] \text{ [Dividing each side by 5] } \\[1em] \Rightarrow y = \frac{30}{5} \\[1em] \Rightarrow y = 6.\end{aligned}$$

Hence, $\bm{y = 6}$.

12Exercise 13(B)

Solve:

$\frac{x}{2} + 2 = 5 - x$

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Solving,

$$\begin{aligned}\Rightarrow \frac{x}{2} + 2 = 5 - x \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{x}{2} + x = 5 - 2 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{x + 2x}{2} = 3 \\[1em] \Rightarrow \frac{3x}{2} = 3 \\[1em] \text{ [Multiplying each side by 2] } \\[1em] \Rightarrow 3x = 6 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow x = \frac{6}{3} \\[1em] \Rightarrow x = 2.\end{aligned}$$

Hence, $\bm{x = 2}$.

13Exercise 13(B)

Solve:

$6(2x - 1) - 5(x - 3) = 2(x + 2)$

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Solving,

$$\begin{aligned}\Rightarrow 6(2x - 1) - 5(x - 3) = 2(x + 2) \\[1em] \text{ [Removing brackets] } \\[1em] \Rightarrow 12x - 6 - 5x + 15 = 2x + 4 \\[1em] \Rightarrow 7x + 9 = 2x + 4 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 7x - 2x = 4 - 9 \\[1em] \Rightarrow 5x = -5 \\[1em] \text{ [Dividing each side by 5] } \\[1em] \Rightarrow x = \frac{-5}{5} \\[1em] \Rightarrow x = -1.\end{aligned}$$

Hence, $\bm{x = -1}$.

14Exercise 13(B)

Solve:

$7(3x - 1) - 6(2x + 3) = 8(x - 2) + 1$

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Solving,

$$\begin{aligned}\Rightarrow 7(3x - 1) - 6(2x + 3) = 8(x - 2) + 1 \\[1em] \text{ [Removing brackets] } \\[1em] \Rightarrow 21x - 7 - 12x - 18 = 8x - 16 + 1 \\[1em] \Rightarrow 9x - 25 = 8x - 15 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 9x - 8x = -15 + 25 \\[1em] \Rightarrow x = 10.\end{aligned}$$

Hence, $\bm{x = 10}$.

11 Mark · Exercise 13(C) - Multiple Choice Questions

5 less than thrice $x$ is

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Thrice $x = 3x$.

5 less than thrice $x$ means 5 is subtracted from $3x$, i.e., $3x - 5$.

Hence, option 2 is the correct option.

21 Mark · Exercise 13(C) - Multiple Choice Questions

If $5x + 8 = 4$, then $3x$ = ?

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Solving,

$$\begin{aligned}\Rightarrow 5x + 8 = 4 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 5x = 4 - 8 \\[1em] \Rightarrow 5x = -4 \\[1em] \text{ [Dividing each side by 5] } \\[1em] \Rightarrow x = \frac{-4}{5}.\end{aligned}$$

∴ $3x = 3 \times \frac{-4}{5} = \frac{-12}{5}$

Hence, option 3 is the correct option.

31 Mark · Exercise 13(C) - Multiple Choice Questions

If $3m - 8 = -4$, then $m$ = ?

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Solving,

$$\begin{aligned}\Rightarrow 3m - 8 = -4 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 3m = -4 + 8 \\[1em] \Rightarrow 3m = 4 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow m = \frac{4}{3}.\end{aligned}$$

Hence, option 4 is the correct option.

41 Mark · Exercise 13(C) - Multiple Choice Questions

If $4x + 3 = 15$, then $2x - 3$ = ?

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Solving,

$$\begin{aligned}\Rightarrow 4x + 3 = 15 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 4x = 15 - 3 \\[1em] \Rightarrow 4x = 12 \\[1em] \text{ [Dividing each side by 4] } \\[1em] \Rightarrow x = \frac{12}{4} = 3.\end{aligned}$$

∴ $2x - 3 = 2 \times 3 - 3 = 6 - 3 = 3$

Hence, option 3 is the correct option.

51 Mark · Exercise 13(C) - Multiple Choice Questions

If $\frac{m}{3} + 2 = 5$, then $m$ = ?

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Solving,

$$\begin{aligned}\Rightarrow \frac{m}{3} + 2 = 5 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{m}{3} = 5 - 2 \\[1em] \Rightarrow \frac{m}{3} = 3 \\[1em] \text{ [Multiplying each side by 3] } \\[1em] \Rightarrow m = 3 \times 3 = 9.\end{aligned}$$

Hence, option 2 is the correct option.

61 Mark · Exercise 13(C) - Multiple Choice Questions

If $\frac{x}{2} + 3 = 5 - x$, then $x$ = ?

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Solving,

$$\begin{aligned}\Rightarrow \frac{x}{2} + 3 = 5 - x \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{x}{2} + x = 5 - 3 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{x + 2x}{2} = 2 \\[1em] \Rightarrow \frac{3x}{2} = 2 \\[1em] \text{ [Multiplying each side by 2] } \\[1em] \Rightarrow 3x = 4 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow x = \frac{4}{3}.\end{aligned}$$

Hence, option 1 is the correct option.

71 Mark · Exercise 13(C) - Multiple Choice Questions

If $\frac{x}{2} - 5 = \frac{x}{3} - 6$, then $x$ = ?

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Solving,

$$\begin{aligned}\Rightarrow \frac{x}{2} - 5 = \frac{x}{3} - 6 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{x}{2} - \frac{x}{3} = -6 + 5 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{3x - 2x}{6} = -1 \\[1em] \Rightarrow \frac{x}{6} = -1 \\[1em] \text{ [Multiplying each side by 6] } \\[1em] \Rightarrow x = -6.\end{aligned}$$

Hence, option 2 is the correct option.

81 Mark · Exercise 13(C) - Multiple Choice Questions

If $\frac{x}{3} - \frac{x}{4} = 5$, then $x$ = ?

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Solving,

$$\begin{aligned}\Rightarrow \frac{x}{3} - \frac{x}{4} = 5 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{4x - 3x}{12} = 5 \\[1em] \Rightarrow \frac{x}{12} = 5 \\[1em] \text{ [Multiplying each side by 12] } \\[1em] \Rightarrow x = 60.\end{aligned}$$

Hence, option 3 is the correct option.

91 Mark · Exercise 13(C) - Multiple Choice Questions

If $4x - 1 = 7$, then $3x - 2$ = ?

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Solving,

$$\begin{aligned}\Rightarrow 4x - 1 = 7 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 4x = 7 + 1 \\[1em] \Rightarrow 4x = 8 \\[1em] \text{ [Dividing each side by 4] } \\[1em] \Rightarrow x = \frac{8}{4} = 2.\end{aligned}$$

∴ $3x - 2 = 3 \times 2 - 2 = 6 - 2 = 4$

Hence, option 2 is the correct option.

101 Mark · Exercise 13(C) - Multiple Choice Questions

If $\frac{2x}{2} - 8 = 2 - x$, then $x$ = ?

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Solving,

$$\begin{aligned}\Rightarrow \frac{2x}{2} - 8 = 2 - x \\[1em] \Rightarrow x - 8 = 2 - x \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow x + x = 2 + 8 \\[1em] \Rightarrow 2x = 10 \\[1em] \text{ [Dividing each side by 2] } \\[1em] \Rightarrow x = \frac{10}{2} = 5.\end{aligned}$$

Hence, option 1 is the correct option.

1Exercise 13(C) - Mental Maths

Fill in the blanks:

(i) The sum of a number and 6 is 15. The number is ...............

(ii) If $\frac{5x}{7} - \frac{3x}{2} = \frac{11}{14}$, then $x$ = ...............

(iii) If $\frac{5x}{6} - \frac{2x}{3} = 9$, then $x$ = ...............

(iv) If $5(3 − 2x) − 3(5 − 3x) = 6$, then $x$ = ...............

(v) If $\frac{x}{3} - 3 = 3$, then $x$ = ...............

(vi) If 3 more than one-third of a number is 5, then we write it as ...............

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(i) Let the number be $x$.

$$\begin{aligned}\Rightarrow x + 6 = 15 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow x = 15 - 6 \\[1em] \Rightarrow x = 9.\end{aligned}$$

Hence, the number is 9.

(ii) Solving,

$$\begin{aligned}\Rightarrow \frac{5x}{7} - \frac{3x}{2} = \frac{11}{14} \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{10x - 21x}{14} = \frac{11}{14} \\[1em] \Rightarrow \frac{-11x}{14} = \frac{11}{14} \\[1em] \text{ [Equating numerators] } \\[1em] \Rightarrow -11x = 11 \\[1em] \text{ [Dividing each side by −11] } \\[1em] \Rightarrow x = -1.\end{aligned}$$

Hence, $\bm{x = −1}$.

(iii) Solving,

$$\begin{aligned}\Rightarrow \frac{5x}{6} - \frac{2x}{3} = 9 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{5x - 4x}{6} = 9 \\[1em] \Rightarrow \frac{x}{6} = 9 \\[1em] \text{ [Multiplying each side by 6] } \\[1em] \Rightarrow x = 54.\end{aligned}$$

Hence, $\bm{x = 54}$.

(iv) Solving,

$$\begin{aligned}\Rightarrow 5(3 - 2x) - 3(5 - 3x) = 6 \\[1em] \text{ [Removing brackets] } \\[1em] \Rightarrow 15 - 10x - 15 + 9x = 6 \\[1em] \Rightarrow -x = 6 \\[1em] \text{ [Multiplying each side by −1] } \\[1em] \Rightarrow x = -6.\end{aligned}$$

Hence, $\bm{x = −6}$.

(v) Solving,

$$\begin{aligned}\Rightarrow \frac{x}{3} - 3 = 3 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{x}{3} = 3 + 3 \\[1em] \Rightarrow \frac{x}{3} = 6 \\[1em] \text{ [Multiplying each side by 3] } \\[1em] \Rightarrow x = 18.\end{aligned}$$

Hence, $\bm{x = 18}$.

(vi) Solving,

Let the number be $x$.

One-third of the number = $\frac{x}{3}$

3 more than one-third of the number = $\frac{x}{3} + 3$

∴ The statement is written as $\frac{x}{3} + 3 = 5$.

Hence, the required equation is $\bm{\frac{x}{3} + 3 = 5}$.

2Exercise 13(C) - Mental Maths

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

(i) If $\frac{4x}{3} + 3 = x - 2$, then $x$ = 15 ...............

(ii) If $\frac{3y}{2} - 5 = -7$, then $y = \frac{4}{3}$ ...............

(iii) If $2x + 3x + 4x = 5x + 1$, then $x = \frac{1}{4}$ ...............

(iv) If $\frac{x}{5} + 4 = 5$, then $x$ = −5 ...............

(v) If $−6 + 3x$ = −5, then $x = \frac{1}{3}$ ...............

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(i) Solving,

$$\begin{aligned}\Rightarrow \frac{4x}{3} + 3 = x - 2 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{4x}{3} - x = -2 - 3 \\[1em] \text{ [Taking L.C.M.] } \\[1em] \Rightarrow \frac{4x - 3x}{3} = -5 \\[1em] \Rightarrow \frac{x}{3} = -5 \\[1em] \text{ [Multiplying each side by 3] } \\[1em] \Rightarrow x = -15.\end{aligned}$$

Since $x$ = −15 and not 15, the given statement is false.

Hence, the given statement is false (F).

(ii) Solving,

$$\begin{aligned}\Rightarrow \frac{3y}{2} - 5 = -7 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{3y}{2} = -7 + 5 \\[1em] \Rightarrow \frac{3y}{2} = -2 \\[1em] \text{ [Multiplying each side by 2] } \\[1em] \Rightarrow 3y = -4 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow y = \frac{-4}{3}.\end{aligned}$$

Since $y = \frac{-4}{3}$ and not $\frac{4}{3}$, the given statement is false.

Hence, the given statement is false (F).

(iii) Solving,

$$\begin{aligned}\Rightarrow 2x + 3x + 4x = 5x + 1 \\[1em] \Rightarrow 9x = 5x + 1 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 9x - 5x = 1 \\[1em] \Rightarrow 4x = 1 \\[1em] \text{ [Dividing each side by 4] } \\[1em] \Rightarrow x = \frac{1}{4}.\end{aligned}$$

Since $x = \frac{1}{4}$, the given statement is true.

Hence, the given statement is true (T).

(iv) Solving,

$$\begin{aligned}\Rightarrow \frac{x}{5} + 4 = 5 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow \frac{x}{5} = 5 - 4 \\[1em] \Rightarrow \frac{x}{5} = 1 \\[1em] \text{ [Multiplying each side by 5] } \\[1em] \Rightarrow x = 5.\end{aligned}$$

Since $x$ = 5 and not −5, the given statement is false.

Hence, the given statement is false (F).

(v) Solving,

$$\begin{aligned}\Rightarrow -6 + 3x = -5 \\[1em] \text{ [By transposition] } \\[1em] \Rightarrow 3x = -5 + 6 \\[1em] \Rightarrow 3x = 1 \\[1em] \text{ [Dividing each side by 3] } \\[1em] \Rightarrow x = \frac{1}{3}.\end{aligned}$$

Since $x = \frac{1}{3}$, the given statement is true.

Hence, the given statement is true (T).

1Exercise 13(C) - Assertion-Reason Questions

Assertion (A): The equation $3x − 4 = 2 + x$ can also be written as $3x − x = 2 + 4$.

Reason (R): Any term of an equation can be shifted to the other side with change in its sign.

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In the equation $3x − 4 = 2 + x$, on transposing −4 to R.H.S. it becomes +4 and on transposing $x$ to L.H.S. it becomes −$x$.

$$\begin{aligned}\Rightarrow 3x - 4 = 2 + x \\[1em] \Rightarrow 3x - x = 2 + 4.\end{aligned}$$

So, Assertion (A) is true.

Any term of an equation can indeed be shifted to the other side with change in its sign. This is the rule of transposition, which is exactly the rule used above. So, Reason (R) is true and it is the correct explanation of Assertion (A).

Hence, option 1 is the correct option.

2Exercise 13(C) - Assertion-Reason Questions

Assertion (A): $x$ = 2 is the solution of the equation $\frac{6x}{2} + 3 = 3x$

Reason (R): The solution of the equation satisfies the equation.

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Putting $x$ = 2 in the given equation,

$$\begin{aligned}\text{L.H.S.} = \frac{6 \times 2}{2} + 3 = 6 + 3 = 9 \\[1em] \text{R.H.S.} = 3 \times 2 = 6.\end{aligned}$$

Since L.H.S. ≠ R.H.S., $x$ = 2 is not the solution of the given equation.

In fact, on simplifying the equation we get $3x + 3 = 3x$, i.e., 3 = 0, which is not possible. So, the equation has no solution. Assertion (A) is false.

The solution (root) of an equation is the value of the variable which makes L.H.S. = R.H.S., i.e., it satisfies the equation. So, Reason (R) is true.

Hence, option 4 is the correct option.

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