2013 CSAT, all questions
UPSC Prelims 2013 · CSAT
Question 62: Basic Numeracy
A sum of ₹ 700 has to be used to give seven cash prizes to the students of a school for their overall academic performance. If each prize is ₹ 20 less than its preceding prize, what is the least value of the prize ?
a₹ 30
b₹ 40
c₹ 60
d₹ 80
AnswerUPSC’s answer is (b).
Seven prizes each fall by 20, so if the least prize is L the prizes are L, L + 20, L + 40, up to L + 120. Their sum is 7L + 20 x (1 + 2 + 3 + 4 + 5 + 6) = 7L + 420 = 700, so 7L = 280 and L = 40. Check: 40, 60, 80, 100, 120, 140 and 160 add up to 700.
Why each option is right or wrong
- (a) Wrong. A least prize of 30 gives a total of 630.
- (b) Right. 7 x 40 + 420 = 700.
- (c) Wrong. A least prize of 60 gives a total of 840.
- (d) Wrong. A least prize of 80 gives a total of 980.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.