UPSC Prelims 2019 · CSAT
Question 39: Basic Numeracy
Rakesh had money to buy 8 mobile handsets of a specific company. But the retailer offered very good discount on that particular handset. Rakesh could buy 10 mobile handsets with the amount he had. What was the discount the retailer offered ?
AnswerUPSC’s answer is (b).
Let the original price be 1 per handset, so Rakesh's money is 8. At the new price the same 8 buys 10 handsets, so the new price is 8 / 10 = 0.8. That is a fall of 0.2 on 1, a 20% discount. The discount is measured on the original price; the 25% rise in handsets (8 to 10) is not the discount.
Why each option is right or wrong
- (a) Wrong: 15% gives a price of 0.85, buying about 9.4 handsets.
- (b) Right: the price falls from 1 to 0.8.
- (c) Wrong: 25% is the rise in handsets from 8 to 10, not the discount.
- (d) Wrong: 30% gives a price of 0.7, buying about 11.4 handsets.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2019, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.