UPSC Prelims 2022 · CSAT
Question 47: Basic Numeracy
A person X wants to distribute some pens among six children A, B, C, D, E and F. Suppose A gets twice the number of pens received by B, three times that of C, four times that of D, five times that of E and six times that of F. What is the minimum number of pens X should buy so that the number of pens each one gets is an even number?
AnswerUPSC’s answer is (c).
The shares satisfy A = 2B = 3C = 4D = 5E = 6F. A must be a multiple of the LCM of 2 to 6, which is 60. For A = 60: B = 30, C = 20, D = 15, E = 12, F = 10, a total of 147. But D = 15 is odd. Doubling gives A = 120, B = 60, C = 40, D = 30, E = 24, F = 20, all even, with total 294.
Why each option is right or wrong
- (a) 147 gives D = 15 pens, which is odd.
- (b) 150 would make A = 61.2, not a whole number.
- (c) Correct: 120 + 60 + 40 + 30 + 24 + 20 = 294.
- (d) 300 would make A about 122.4, not a whole number.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2022, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.