2022 CSAT, all questions
UPSC Prelims 2022 · CSAT
Question 20: Basic Numeracy
The increase in the price of a certain item was 25%. Then the price was decreased by 20% and then again increased by 10%. What is the resultant increase in the price?
a5%
b10%
c12·5%
d15%
AnswerUPSC’s answer is (b).
Use multipliers: +25% is 1.25, −20% is 0.80 and +10% is 1.10. Then 1.25 × 0.80 = 1.00, and 1.00 × 1.10 = 1.10. The price ends 10% above the original. Successive percentage changes multiply; they do not add (25 − 20 + 10 = 15 is the trap). Check with a base of 100: it goes to 125, then to 100, then to 110, a net rise of 10 points.
Why each option is right or wrong
- (a) 5% matches no combination of the three changes.
- (b) Correct: 1.25 × 0.8 × 1.1 = 1.1, a 10% rise.
- (c) 12.5% does not come from multiplying the three changes.
- (d) 15% is the trap of adding the percentages (25 − 20 + 10).
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2022, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.