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One pump can fill a gasoline tank in 9 hours.
With a second pump working simutaneously the tank can be filled in 5 hours.
How long would it take the second pump to fill the tank operating alone?
Let x = 2nd pump time working alone
Let the completed job (full tank) = 1
A typical shared work equation
multiply equation by 9x, results
5x + 9(5) = 9x
5x + 45 = 9x
45 = 9x - 5x
45 = 4x
x = 11.25 hrs, 2nd pump by itself
.56 + .44 = 1