One water pump can fill half of a certain empty tank in 7 hours. Another pump can fill half of the same tank in 7.5 hours. Working together, how long will it take these two pumps to fill the entire tank?	Options:	A) 7 7/13	B) 1 5/8	C) 3 1/4	D) 7 7/29	E) 3 1/2
One pump can fill a tank in 7 hours and another in 7.5 hours   so the rate at which both can half fill the tank is (1/7+1/7.5) =&gt; 29/105   Thus half of the tank can be filled in 105/29   so for filling the complete tank =&gt; 105/29*2 = 210/29 =7 7/29   ANSWER:7 7/29
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One water pump can fill half of a certain empty tank in 7 hours. Another pump can fill half of the same tank in 7.5 hours. Working together, how long will it take these two pumps to fill the entire tank?