A can do a work in 15 days and B in 20 days. If they on it together for 4 days, then the fraction of the work that is left is:

A 1/4

B 1/8

C 1/15

D 8/15

Correct Answer: Option D

Solution:

(A+B)'s 1 day's work = 1/15 + 1/20 = (4+3)/60 = 7/60 part.

So, (A+B)'s 4 day's work = 7/60 \( \times \) 4 or 7/15 part.

So, Work left 1- 7/15 = 8/15 part.