Question

if a can do a piece of work in 4 days b can do it in 5 days. with the assistance of c they completed the work in 2 days. find in how many days can c alone do it

Answer 1

1. Given a=1/4 and b=1/5
2. with the assistance of c they completed the work in 2 days.hence a+b+c completed work in 2 days
3. 2(a+b+c)=1
4. on substituting a and b we get 2((1/4)+(1/5)+(1/x))=1
5. from this we get x=20 which is c can complete work alone in 20 days