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Railways PYQCBT 1 2016

RRB NTPC · Question 47

Adil and Biren together can complete a task in 20 days. Biren and Chirag together can complete the same task in 50 days. Adil and Chirag together can complete the same task in 40 days. If the same task was to be done by them alone, what would be the ratio of time taken by Adil alone to taken by Biren? A. 11 : 9 B. 11 : 3 C. 7 : 9 D. 9 : 11

  1. D

  2. A

  3. B

  4. C

Show answer & explanation

Answer: (A) D

Explanation

A + B = 1/20, B + C = 1/50 and A + C = 1/40 of the task per day. Together A + B + C = (1/20 + 1/50 + 1/40)/2 = 19/400. So A = 19/400 − 1/50 = 11/400 and B = 19/400 − 1/40 = 9/400. Times are in the inverse ratio: A : B = 9 : 11.