UPSC Prelims 2001 · General Studies
Question 114: Data Interpretation
The following table shows the percentage change in the consumption of electricity by five towns P, Q, R, S, T from 1986 to 1988: Town Per cent change from 1986 to 1987 From 1987 to 1988 P +8 −18 Q +15 −11 R +6 +9 S −7 −5 T +13 −6 If town T consumed 500,000 units in 1986, how much did it consume in 1988?
AnswerThe answer is (b).
Town T consumed 500,000 units in 1986. A 13 per cent rise for 1987 gives 500,000 x 1.13 = 565,000. A 6 per cent fall for 1988 gives 565,000 x 0.94 = 531,100 units. Remember that successive percentage changes multiply; adding +13 and -6 to get +7 per cent would give 535,000, which is wrong.
Why each option is right or wrong
- (a) 371,000 is far below the starting value, though consumption rose overall.
- (b) Right: 500,000 x 1.13 x 0.94 = 531,100.
- (c) 551,100 does not follow from the successive changes.
- (d) 571,100 does not follow from the successive changes.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2001, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.