Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill cistern. How much time will be taken by A to fill the cistern separately?

A. 1 hr
B. 2 hrs
C. 6 hrs
D. 8 hrs

Explanation:

Let the cistern be filled by pipe A alone in x hours.

Then, pipe B will fill it in (x + 6) hours.
1/x + 1/(x + 6) = 1/4
x2 – 2x – 24 = 0
(x – 6)(x + 4) = 0 => x = 6.

Correct Answer: 6 hrs ✔

Last Updated: February 08, 2020