Multiple choice

X, Y and Z takes 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 the work in 60 days, how will it take Z to complete the work alone?

  1. 78

  2. 90

  3. 96

  4. 114

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Combined work rate of X, Y, Z is 1/18. X's rate is 1/36, Y's rate is 1/60. Z's rate = 1/18 - 1/36 - 1/60 = 10/180 - 5/180 - 3/180 = 2/180 = 1/90. Therefore, Z alone takes 90 days to complete the work.