1.  A can finish a work in 18 days and B can do the same work in 15 days. B worked for 10 days and left the job. In how many days, A alone can finish the remaining work?
A. 5
B. 51/2
C. 6
D. 8

Answer: Option C

Explanation:

B's 10 day's work = ( 1 x 10 ) = 2 .
15 3

Remaining work = ( 1 - 2 ) = 1 .
3 3

Now, 1 work is done by A in 1 day.
18

Therefore 1 work is done by A in ( 18 x 1 ) = 6 days.
3 3