A and B together can complete a job in 8 days. Both B and C, working alone can finish the same job in 12 days. A and B commence work on the job

A and B together can complete a job in 8 days. Both B and C, working alone can finish the same job in 12 days. A and B commence work on the job, and work for 4 days, whereupon A leaves. B continues for 2 more days, and then he leaves too. C now starts working, and finishes the job. How many days did C require?

a)            5

b)            8

c)            3

d)            4

Sol:

Now ATQ,

4 days work of A and B = 4 × 9 = 36

2 days work of B = 2 × 6 = 12

Remaining work = 72 – (36 + 12) = 24