A and B can complete a work in 20 days and 30 days respectively. If they work together for 10 days,

A. 1/3

B. 1/4

C. 1/2

D. 1/5

E. None of the above

Answer: A. 1/3

In 10 days, A and B together complete 10(1/20 + 1/30) = 10(1/12) = 5/6 of the work, leaving 1/6 of the work.

Posted in: Time & Work - Aptitude - Mathematics