Question

7. A can do work in 15 days and B in 20 days. If they
work on it together for 4 days, then the fraction of
the work that is left is
(ACC 2015)
(b) 1/10 (c) 7/15
(d) 8/15
(a) 1/4​

Answer 1

Answer:

A finishes the work in 15 days.

So in 1 day, A finishes 1/15 work.

Similarly, B finishes 1/20 work in 1 day.

When they work together, they will be able to finish

1/15 +1/20 =7/60 work in 1 day.

As mentioned in question, in 4 days, they will finish 4* 7/60

Or 7/15 work

So the remaining work is 1–7/15 or 8/15