One top can fill a cistern in 2 hours and another can empty the cistern in 3 hours. How long will they take to fill the cistern if both the taps are opened?

A. 5 Hours
B. 6 Hours
C. 7 Hours
D. 8 Hours

Explanation:

Net filling in 1 hour = (1/2 – 1/3) = 1/6

Time taken to fill the cistern = 6 hours