A is thrice as good a workman as B and so takes 40 days less than B for doing a job. The time in which they can do the job together is -

Question: A is thrice as good a workman as B and so takes 40 days less than B for doing a job. The time in which they can do the job together is -

Solution:
Let A alone takes x days
and B alone takes 3x days to complete the job.

ATQ,
3x - x = 40
⇒ 2x = 40
⇒ x = 20

So, A alone takes 20 days and B alone takes 3 × 20 = 60 days to complete the job.

(A + B)'s 1 days work = (1/20 + 1/60) = 1/15 part

∴ A and B together can do the work in 15 days.