Question

Ram can do work in 15 days and mohan can do the same work in 20 days. they both work together for 4 days and both leave the work. what fraction of work is left now?

Answer 1

1 day work of Ram = 1/15

1 day work of Mohan = 1/20

1 day work of Ram and Mohan together = 1/15 + 1/20 = (4+3)/60 = 7/60

Work done in 4 days = 4 * 7/60 = 28/60 = 7/15

Work left = 1 - 7/15 = 8/15

8/15 of work is still remaining.

Answer 2

Given:

Days taken by Ram to complete the work = 15

Days taken by Mohan to complete the work = 20

Days they both do the work = 4

To find:

The fraction of work left

Solution:

Ram's one day work  = 1/15

Mohan's one day work  = 1/20

Thus,

Days when Ram and Mohan both can work together -

= 1/15 + 1/20

= 4 + 3/60

= 7/60

Now, since the work is done in 4 days,

Thus,

= 4 × 7/60

= 2 × 7/30

= 7/15

Therefore, work left

= 1 - 7/15

= 8/15

Answer: The fraction of work still left is 8/15 .