P and Q together can complete a piece of work in 6 days. If P can alone complete the work in 18 days, then the number of days required for Q to finish the work is:
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 9 days.
Total work (LCM of 6, 18) = 18
The efficiency of P and Q = 18/6 = 3
The efficiency of P = 18/18 = 1
So, the efficiency of Q = 3 - 1 = 2
Hence, the time taken by Q to do the work alone = 18/2= 9 days.