2021 CSAT, all questions
UPSC Prelims 2021 · CSAT
Question 54: Basic Numeracy
P scored 40 marks more than Q in an examination. If Q scored 10% less marks than P, then how much did Q score ?
a360
b380
c400
d420
AnswerUPSC’s answer is (a).
Q scored 10% less than P, so Q = 0.9P. Also P = Q + 40. So P = 0.9P + 40, giving 0.1P = 40 and P = 400. Then Q = 400 − 40 = 360, which is 90% of 400. Remember: express both relationships in terms of one unknown, and take the percentage on P, the number it is stated against, not on Q.
Why each option is right or wrong
- (a) Right: P = 400 and Q = 0.9 × 400 = 360, which is 40 less than P.
- (b) 380 would make P = 420, but 380 is about 90.5% of 420, not 90%.
- (c) 400 is P's score, not Q's.
- (d) 420 would make P = 460, but 420 is about 91% of 460, not 90%.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.