A alone can do a job in 12 days, B alone in 24 days. They work together for 4 days, then A leaves. In how many more days will B finish the job?
Show answer & explanation
Correct answer: A
Explanation
Given:
A works = 12 days
B works = 24 days
Both work together = 4 days
A's work rate = 1/12
B's work rate = 1/24
(A + B)'s work rate = 1/12 + 1/24 = 1/8
Work done in 4 days = 4 × 1/8 = 1/2
Remaining work = 1 − 1/2 = 1/2
Now B will work alone
B's work rate = 1/24
Time = (1/2) ÷ (1/24) = 12 days