It takes four hours for two pipes A and B to fill a cistern. If they had been opened independently, it would have taken B 6 hours longer to fill the cistern than A. A will need how much time to fill the cistern separately?
A. 1hour
B. 2hour
C. 6hour
D. 8hour
Answer:C
It takes four hours for two pipes A and B to fill a cistern. If they had been opened independently, it would have taken B 6 hours longer to fill the cistern than A. A will need how much time to fill the cistern separately?
A. 1hour B. 2hour C. 6hour D. 8hour
Explanation: Allow x hours for pipe A to fill the cistern alone.Then, in (x + 6) hours, pipe B will fill it.1/4 = 1/x + 1/(x + 6),1/4 = x + 6 + x/x(x + 6),2x - 24 = 0 x2 - 2x - 24 = 0 x2 - 2x - 24 =0 = (x -6)(x + 4)[ignoring the negative value of x] x = 6.