2019 CSAT, all questions
UPSC Prelims 2019 · CSAT
Question 34: Basic Numeracy
In an examination, A has scored 20 marks more than B. If B has scored 5% less marks than A, how much has B scored ?
a360
b380
c400
d420
AnswerUPSC’s answer is (b).
Let A's score be x. B has 20 less, and that is also 5% less than A: 0.95x = x - 20, so 0.05x = 20 and x = 400. B scored 400 - 20 = 380. Check: 5% of 400 is 20, so B is 5% below A. The 20-mark gap is exactly the 5% of A's score that B lacks.
Why each option is right or wrong
- (a) Wrong: 360 is 40 less than 400, not 20.
- (b) Right: A = 400, B = 380.
- (c) Wrong: 400 is A's score.
- (d) Wrong: 420 would be above A's score.
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.