Question

A,B and C can do a piece of work in 10,9 and 15 days respectively. they started the work together but C left after 2 days. in how many days will the remaining work be completed by A and B?

Answer 1

A can do one piece of work (100% of work) in 10 days =>

A can do (1/10) of work in 1 day

Similarly, B can do (1/9) of work in 1 day

C can do (1/15) of work in 1 day

A,B,C together can complete (1/10) + (1/9) + (1/15) of work

i.e. 25/90 = 5/18 of work in one day

In 2 days, 10/18 = 5/9 of work is completed.

As C left after 2 days, remaining 4/9 of work has to be completed by A+B

A+B one day's work = (1/10) + (1/9)

= 19/90

So, A+B can complete 100% work in 90/19 days

But we need only (4/9) of work.

So, remaining work will be completed by A+B in (4/9)*(90/19) = 2 (1/19) days

Regards,

KKKoppu