Question

A can do a piece of work in 20 days. he works at it for 5 days and then b finishes it in 10 more days. in how many days will a and b together finish the work?

Answer 1

work done by A in 5 days = 1/20*5
                                         =1/4
remaining work=(1-1/4)
                        =3/4
now,3/4 work is done by B in 10 days
whole work will be done by B in 10*4/3= 40/3 days
as 1 day's work of A = 1/20 
1 day's work of B =3/40
(A+B)'s 1 day's work= 1/20+3/40
                                = 1/8
so,both finished the work in 8 day's.

Answer 2

Step-by-step explanation:

For 20 days=20 units of work is done.

For 5 days=5 units of work is done .

Outoff 20 days ,15 days work of A is done by B in 10 days

So, per day work of B =15/10=1.5

And we had assumed per day work of A is 1 unit.

So, together per day work of A and B is 1+1.5=2.5

No. Of days A and B if together work=

Total unit of work/per day work of both

20/2.5=8