2020 CSAT, all questions
UPSC Prelims 2020 · CSAT
Question 18: Basic Numeracy
Consider the following data :
| Average marks in English | Average marks in Hindi | |
|---|---|---|
| Girls | 9 | 8 |
| Boys | 8 | 7 |
| Overall average marks | 8·8 | x |
What is the value of x in the above table?
a7·8
b7·6
c7·4
d7·2
AnswerUPSC’s answer is (a).
Weight each subject's average by the share of girls and boys. For English, girls average 9 and boys 8 with an overall 8.8, so the girls' share g satisfies 8 + g = 8.8, giving g = 0.8 (boys 0.2). The same class sits for Hindi: 0.8 × 8 + 0.2 × 7 = 6.4 + 1.4 = 7.8.
Why each option is right or wrong
- (a) Right: 0.8 × 8 + 0.2 × 7 = 7.8.
- (b) 7.6 would need 60% girls, not 80%.
- (c) 7.4 would need 40% girls.
- (d) 7.2 would need 20% girls.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.