If A and B together complete a work in 12 days and B alone can do it in 20 days, how many days will A alone take to complete the work?
If A and B together complete a work in 12 days and B alone can do it in 20 days, how many days will A alone take to complete the work?
Explanation
Let's denote A's rate of work as A, and B's rate of work as B.
Given A + B together complete the work in 12 days:
(A + B)'s 1 day's work = 1/12
B alone completes the work in 20 days:
B's 1 day's work = 1/20
A's 1 day's work = (A + B)'s 1 day's work - B's 1 day's work
= 1/12 - 1/20
= (5 - 3) / 60
= 2 / 60
= 1 / 30
A alone will complete the work in 30 days.