Question

Two pipes A and B can separately fill a cistern in 24
and 32 minutes respectively. They started to fill a
cistern together, but B is turned off after few minutes
and A fills the rest of the cistern. If total time taken is 18
minutes, after how many minutes is tap B turned off?

Answer 1

first A,B together work
next unknow work X by togerther work, add X-18 by b capacity equal to 1
simplify

Answer 2

we can use the formula d= r*t. we will be more flexible about d,
1 cistern = (rate to fill up ) * 24 minutes

Answer 3

let rA = speed at which pipe A can fill up 1 cistern. , rB = speed at which pipe B can fill up 1 cistern .
rA = 1/24 , rB = 1/32
now they work together to fill up 1 cistern, pipe A is fillup the full time of 18 minutes but pipe B is turned off
1 = rA * 18 + rB * t
1 = 1/24 * 18 + 1/32 * t

Answer 4

or better yet, rA is the speed at which it fills cisterns

Answer 5

ok , if you have any questions let me know :) take care

Answer 6

I get t = 8 minutes, so it was turned off after 8 minutes

Answer 7

so it is turned off for 10 minutes

Answer 8

This looks correct.

Answer 9

So the answer would be: it was turned off after 8 minutes. Good Job @perl