UPSC Prelims 1998 · General Studies
Question 57: Geography
When there is noon at the G.M.T. meridian, people at another place of the Earth are taking their 6 o’clock morning tea. The longitude of the place is
AnswerThe answer is (d).
The Earth turns 360 degrees in 24 hours, so every 15 degrees of longitude is one hour. A place where the clock reads 6 am when it is noon at Greenwich is six hours behind, and so lies west of Greenwich by 6 x 15 = 90 degrees: 90 degrees W. Places east are ahead: 17 degrees 30' E would read about 1:10 pm, 7 degrees 30' W about 11:30 am, and 172 degrees 30' E about 11:30 pm.
Why each option is right or wrong
- (a) 17 degrees 30' E is ahead of Greenwich, giving about 1:10 pm.
- (b) 7 degrees 30' W is only 30 minutes behind, giving 11:30 am.
- (c) 172 degrees 30' E is about 11.5 hours ahead, giving 11:30 pm.
- (d) Right: 90 degrees W is exactly six hours behind Greenwich.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1998, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.