A and B can complete a work in 15 days and 10 days respectively. They started doing the work together but after 2 days B had to leave and A alone completed the remaining work. The whole work was completed in___________?

A. 8 days
B. 10 days
C. 12 days
D. 15 days

(A.+ B)’s 1 day’s work = ( 1/15 + 1/10 ) = 1/6 Work done by A and B in 2 days = ( 1/6 X 2 ) = 1/3 Remaining work = ( 1 – 1/6 ) = 2/3
Now, 1/15 work is done by A in 1 day. so 2/3 work will be done by A in ( 15 X 2/3 ) = 10 days Hence, total time taken = (10 + 2) = 12 days.