1999 General Studies, all questions
UPSC Prelims 1999 · General Studies
Question 3: Geography
If it is 10.00 a.m. I.S.T., then what would be the local time at Shillong on 92°E longitude?
a9.38 a.m.
b10.38 a.m.
c10.22 a.m.
d9.22 a.m.
AnswerThe answer is (b).
Indian Standard Time is based on the 82.5 degrees E meridian. Shillong, at 92 degrees E, lies 9.5 degrees east of it. The Earth turns 1 degree every 4 minutes, so Shillong is 9.5 x 4 = 38 minutes ahead of IST. Local time = 10.00 a.m. + 38 minutes = 10.38 a.m. Remember: places east of a reference meridian are ahead in time, places west of it are behind.
Why each option is right or wrong
- (a) Wrong. This puts Shillong behind IST, but it is east of the IST meridian and so ahead.
- (b) Right. 9.5 degrees east x 4 minutes = 38 minutes ahead of 10.00, which is 10.38 a.m.
- (c) Wrong. 22 minutes ahead would suit a place only 5.5 degrees east of 82.5 degrees E, not 9.5.
- (d) Wrong. 9.22 a.m. is behind IST; Shillong is ahead of it.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1999, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.