Question:
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 the cistern. How much time will be taken by A to fill the cistern separately?
[A].1 hour
2 hours
6 hours
8 hours
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 the cistern. How much time will be taken by A to fill the cistern separately?
[A].
[B].
[C].
[D].
Answer: Option C
Explanation:
Let the cistern be filled by pipe A alone in x hours.
Then, pipe B will fill it in (x + 6) hours.
| 1 | + | 1 | = | 1 | |
| x | (x + 6) | 4 |
| x + 6 + x | = | 1 | |
| x(x + 6) | 4 |
x2 – 2x – 24 = 0
(x -6)(x + 4) = 0
x = 6. [neglecting the negative value of x]