16Hit1600
AlgebraHardTwo pipes filling a tank together

Algebra practice question

One pipe can fill a tank in 6 hours, and a second pipe can fill the same tank in 3 hours. How many hours will the two pipes take to fill the tank together?

Answer: 2

In one hour the pipes fill 1/6 + 1/3 = 1/2 of the tank, so together they take 2 hours.

Common wrong answers

If you answered 9
9 adds the two times.
If you answered 4.5
4.5 averages the two times, which is not how rates combine.
If you answered 1.5
1.5 halves the faster pipe's time without reason.

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