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?
Choose the correct choice from the following options
A) 2
B) 6
C) 4
D) 9
E) 8
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 =&gt; x = 6.   Answer: 6
<result>B</result>
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?