Self Practice Questions

(i) The 0° meridian is known as the Prime Meridian.

(ii) Point A is located at 30°N latitude and 60°E longitude.

The Earth rotates 360° in 24 hours, which means it turns 15° of longitude every hour (360° ÷ 24 = 15°). Therefore, for every 15° of longitude travelled east or west, there is a 1-hour difference in local time.

• If you move eastward, the time increases by 1 hour for every 15°.

• If you move westward, the time decreases by 1 hour for every 15°.

The Prime Meridian (0°) passes through the Royal Astronomical Observatory at Greenwich village, near London. So, in 1884, it was decided by all countries to adopt the local time of Prime Meridian (0°) worldwide.

Hence, when sun is directly overhead at 0° longitude and it is 12 o'clock (noon) there, the international time is calculated east or west of the Prime Meridian with reference to this time.

1. Earth's grid
2. Prime meridian
3. Temperate Zone
4. Tropic of Capricorn

(i)

• The longitude difference: 2° - 0° = 2°
• For 1° longitude difference time difference is 4 minutes.
• So, for 2° longitudinal difference, the time difference is 2° x 4 = 8 minutes.
• As the given place is situated in the east Greenwich, the local time at 2° East will be : 7 a.m. + 8 minutes = 7:08 a.m.

(ii)

• The longitude difference: 25° - 0° = 25°
• For 1° longitudinal difference time difference is 4 minutes.
• So, for 25° longitudinal difference, the time difference is 25° x 4 = 100 minutes or 1 hour 40 minutes.
• Since the given place is situated in the east of Greenwich, the local time at 26° East will be: (7 a.m. + 1 hour 40 minutes) = 8:40 a.m.

• The longitudinal difference: 50° + 13° = 63°
• For 1 longitudinal difference time difference is 4 minutes.
• So, for 63° longitudinal difference, the time difference is 63° x 4 = 252 minutes or 4 hours 12 minutes.
• As the given place is situated in the west of 50° east longitude, the local time at 13° west will be: (11 a.m. - 4 hours 12 minutes) = 6:48 a.m.

• The longitudinal difference: 30° + 30° = 60°.
• For 1° longitudinal difference is 4 minutes.
• So, for 60° longitudinal difference, the time difference is: 60° x 4 = 240 minutes or 4 hours.
• As the given place is situated in the west of 30° East longitude, the local time at 30° west will be: (8 a.m. - 4 hours) = 4 a.m.

• The longitudinal difference between New York and Nigeria is: 75° + 15° = 90°
• For 1° longitudinal difference time difference is 4 minutes.
• So, for 90° longitudinal difference, the time difference is: 90° x 4 = 360 minutes or 6 hours.
• As New York is situated in the west of Nigeria, the local time at New York will be: ( 10 a.m. - 6 hours) = 4 a.m.

• The longitudinal difference: 60° + 90° = 150°
• For 1° longitudinal difference time difference is 4 minutes.
• So, for 150° longitudinal difference, the time difference is 150° x 4 = 600 minutes or 10 hours.
• As the given place is situated in the west of 90° east longitude, the local time at 60° west will be: (5:30 a.m. - 10 hours) = 7:30 p.m. on Thursday.

Calculating time at Prime Meridian (0°) —

• The longitudinal difference: 40° - 0° = 40°
• For 1° longitudinal difference time difference is 4 minutes.
• So, for 40° longitudinal difference, the time difference is 40° x 4 = 160 minutes or 2 hours 40 minutes.
• Since the Prime Meridian (0°) is situated to the east of 40° west longitude, the local time at Prime Meridian (0°) will be: (12 a.m. + 2 hours 40 minutes) = 2:40 a.m.

Calculating time at 50° East longitude or City A —

• The longitudinal difference: 50° - 0° = 50°
• For 1° longitudinal difference time difference is 4 minutes.
• So, for 50° longitudinal difference, the time difference is 50° x 4 = 200 minutes or 3 hours 20 minutes.
• Since the 50° East longitude or City A is situated to the east of Prime Meridian (0°), the local time at City A will be: (2:40 a.m. + 3 hours 20 minutes) = 6 a.m.