A takes 12 days to finish a job, while B takes 36 days to complete the same job. If they collaborate, how many days will it take them to complete the work together?
Show answer & explanation
Correct answer: C
Explanation
A completes the work = 12 days
B completes the work = 36 days
A's work rate = 1/12
B's work rate = 1/36
(A + B)'s work rate = 1/12 + 1/36
= (3 + 1) / 36
= 4/36
= 1/9
Time = 9 days