Question

A, B and C can do a piece of work in 20, 30 and 60 days respectively. In how many days can A do the work if he is assisted by B and C on every third day?

Answer 1

A, B and C working together will finish same piece of work in 10 days

A can do a piece of work in 20 days. That is A is doing the work at a rate of  1 / 20. Therefore

B = 1 / 30

C = 1 / 60

A, B and C working togehter their rate will be added together =

A + B + C =  1 / 20 + 1 / 30 + 1 / 60 = 1 / 10

so they can work together to finish same piece of work in 10 days