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Railways PYQCBT 1 2016

RRB NTPC · Question 63

X, Y and Z take 18 days to complete a piece of work. If X works alone he finishes the work in 36 days and if Y works alone he finishes it in 60 days. How long will it take Z to complete the work alone? A. 78 days B. 90 days C. 96 days D. 14 days

  1. B

  2. A

  3. D

  4. C

Show answer & explanation

Answer: (A) B

Explanation

Z's daily work = 1/18 − 1/36 − 1/60. Over a common denominator of 180: (10 − 5 − 3)/180 = 2/180 = 1/90. So Z alone takes 90 days.