A cistern can be completely drained by a pipe in 6 hours. It can be filled by two pipes in 4 hours and 5 hours, respectively. How many hours

Question

A cistern can be completely drained by a pipe in 6 hours. It can be filled by two pipes in 4 hours and 5 hours, respectively. How many hours will the empty cistern take to fill if all the pipes are running?

If x is the time to fill it, which of the following equations could be used to solve for t?

4x + 5x – 6x = 1
15x + 12x – 10x = 60
4x + 5x = 20

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Answers ( No )

    0
    2022-01-06T00:15:41+00:00

    x/4 +x/5 -x/6=1
    make the denominator the same: 
    15x/60 +12x/60 -10x/60=1
    17x=60
    x=60/17=3.53 hours

    the second choice is the correct answer.

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