One water pump can fill half of a certain empty tank in 4 hours. Another pump can fill half of the same tank in 4.5 hours. Working together, how long will it take these two pumps to fill the entire tank?  Choices
A) 1 7/13 B) 4 5/8 C) 3 1/4 D) 4 4/17 E) 3 1/2
One pump can fill a tank in 4 hours and another in 4.5 hours   so the rate at which both can half fill the tank is (1/4+1/4.5) =&gt; 17/36   Thus half of the tank can be filled in 36/17   so for filling the complete tank =&gt; 36/17*2 = 72/17 =4 4/17   ANSWER:4 4/17
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One water pump can fill half of a certain empty tank in 4 hours. Another pump can fill half of the same tank in 4.5 hours. Working together, how long will it take these two pumps to fill the entire tank?