A can complete work in 25 days and B can complete the same work in 20 days. They started the work together but B left after 4 days and A continued to work. In how many days will the entire work be completed ?

20

A = 25 days, B = 20 days,

⇒ Here, B worked for 4 days, therefore,

⇒ Work done by B in 4 days = 5 x 4 = 20       (Efficiency x Time = Work)

Now, Remaining work = 100 - 20 = 80

Here, remaining work done by A in the whole time(including 4 days),

So, time taken by P to do the work = \(\frac{80}{4}\) = 20 days.

Therefore, the whole work is done in 20 days.