2016 CSAT, all questions
UPSC Prelims 2016 · CSAT
Question 37: Basic Numeracy
Two numbers X and Y are respectively 20% and 28% less than a third number Z. By what percentage is the number Y less than X ?
a12%
b10%
c9%
d8%
AnswerUPSC’s answer is (b).
Take Z = 100. X is 20% less, so X = 80; Y is 28% less, so Y = 72. Y is less than X by 80 - 72 = 8, and as a percentage of X that is 8 / 80 = 10%. Remember: a percentage difference is measured against the number you compare with (here X), not against Z, which would give 8%.
Why each option is right or wrong
- (a) Does not match: 8 as a fraction of 80 is 10%.
- (b) Right: (80 - 72) / 80 = 10%.
- (c) Does not match 8 / 80.
- (d) 8% is the gap measured against Z, not X.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2016, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.