Question 1

Question 1If the time at 0° longitude is 7:00 a.m. what will be the time at(i) 2° East(ii) 25° East longitude.

Accepted Answer

(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.

Question 2

Question 3If the time at 30° East longitude is 8 a.m., what will be the time at 30° west longitude?

Accepted Answer

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.

Question 3

Question 4Calculate the local time in New York (75°W) when it is 10 a.m. in Nigeria (15°E)?

Accepted Answer

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.

Question 4

Question 5What is the time and day at certain place on 60° W longitude when it is 5.30 a.m. on Friday at a place 90° east longitude?

Accepted Answer

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.

Question 5

Question 6Find out the time by studying the following pictorial graph.

Accepted Answer

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.

Question 6

Question 2Greenwich Mean time is taken as reference for international time.

Accepted Answer

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.

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