Pipes A and B can fill a cistern in 15 hours together. But ifthese pipes operate separately A takes 40 hours less than Bto fill the tank. In how many hours the pipe A will fill thecistern working alone?

60

20

40

15

Correct Answer: 20

Explanation:

Let A takes x hours, then B = (x+40) hours

1/x + 1/x+40 = 1/15

x = 20

Question

Pipes A and B can fill a cistern in 15 hours together. But ifthese pipes operate separately A takes 40 hours less than Bto fill the tank. In how many hours the pipe A will fill thecistern working alone?

Accepted Answer

Let A takes x hours, then B = (x+40) hours 1/x + 1/x+40 = 1/15 x = 20