A and B can do work in 6 and 12 days respectively. They began work together but A leaves after 3 days. Then the number of days needed for completion of work is

A. 4

B. 5

C. 6

D. 9

Answer: Option C

Solution(By Examveda Team)

Work done by A in 1 day = 1/6
Work done by B in 1 day = 1/12
Work done by A and B in 1 day 1/6 + 1/12 = 1/4
A and B worked together for the initial 3 days = 3/4
Remaining work = 1/4
Time taken by B to complete this remaining work 1/4 / 1/12 = 3
Total number of days = 3 + 3 = 6