A can finish a job in 10 days, B in 15 days, and C in 20 days. If they all work together for 2 days,

A. 1/3

B. 1/4

C. 1/5

D. 1/6

E. None of the above

Answer: A. 1/3

In 2 days, they complete 2 * (1/10 + 1/15 + 1/20) = 2 * 1/4 = 1/2 of the job. Therefore, 1 - 1/2 = 1/2 of the job is left.

Posted in: Time & Work - Aptitude - Mathematics