UPSC Prelims 2005 · General Studies
Question 96: Basic Numeracy
Left pan of a faulty balance weighs 100 gram more than its right pan. A shopkeeper keeps the weight measure in the left pan while buying goods but keeps it in the right pan while selling his goods. He uses only 1 kg weight measure. If he sells his goods at the listed cost price, what is his gain?
AnswerThe answer is (d).
The left pan is heavier by 100 g. Buying with the 1 kg weight in the left pan, he receives goods weighing 1000 + 100 = 1100 g. Selling with the weight in the right pan, the customer gets 1000 − 100 = 900 g. So he buys 1100 g for the price of 1000 g and sells 1100 g for the price of 1100/900 × 1000 = 1222.2 g. Gain = 222.2/1000 = 200/9 %.
Why each option is right or wrong
- (a) 200 1/11 % is far too large.
- (b) 100/11 % is too small.
- (c) 100/9 % is too small; it ignores one of the two false weighings.
- (d) Correct: 200/9 %.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2005, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.