Question

A and b can do a piece of work in 10 and 15 days respectively. they work together for 5 days and then b leaves. a finishes the remaining work alone. in how many days is the total work finished?

Answer 1

A can do the work in 10 hrs
B can do the work in 15 hrs

in 1 hr A does =1/10
in 1 hr B does =1/15

together in 1 hr they does =(1/10+1/15)=(3+2/30)=5/30=1/6 part

they worked for 5 days
so, work done =(1/6×5)=5/6 part

remaining part = (1-5/6)=1/6 part

work. time
1/6. 3
1. x
x=3/1/6×1
= 3×6×1
= 18