CSAT 2020

Q. A is 16th from the left end in a row or boys and V is 18th from the right end. Q is 11th from A towards the right and 3rd from V towards the right end. How many boys are there in the row?

(a) 40
(b) 41
(c) 42
(d) Cannot be determined due to insufficient data
Correct Answer: (b) 41

Question from UPSC Prelims 2020 CSAT Paper

Explanation :

A is 16th from the left end in a row

Q is 3rd from V towards the right, so position of Q = 18 – 3 = 15th from right end.
Q is 11th from A towards the right, so position of Q = 16 + 11 = 27th from left end.
Hence, total number of boys in the row = 27 + 15 – 1 = 41 (we subtract one because Q has been counted twice)

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