2000 General Studies, all questions
UPSC Prelims 2000 · General Studies
Question 129: Basic Numeracy
A rectangular water tank measures 15 m × 6 m at top and is 10 m deep. It is full of water. If water is drawn out lowering the level by 1 metre, how much of water has been drawn out?
a45,000 litres
b90,000 litres
c4,500 litres
d900 litres
AnswerThe answer is (b).
Lowering the level by 1 metre removes a slab of water with the area of the top: 15 m by 6 m by 1 m is 90 cubic metres. One cubic metre is 1,000 litres, so 90 m cubed is 90,000 litres. The depth of 10 m is only a distraction.
Why each option is right or wrong
- (a) 45,000 litres is half the correct volume.
- (b) Right: 15 x 6 x 1 = 90 cubic metres = 90,000 litres.
- (c) 4,500 litres does not follow from 15 x 6 x 1 = 90 cubic metres.
- (d) 900 litres is far too small, as 90 cubic metres is 90,000 litres.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2000, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.