Two water pumps, working simultaneously at their respective constant rates, took exactly 6 hours to fill a swimming pool. If the constant rate of one pump was 1.5 times the constant rate of the other, how many hours would it have taken the faster pump to fill the pool if it had worked alone at its constant rate?  Answers.
A) 7	B) 8	C) 9	D) 10	E) 11
Let the rate of the slow pump be x. Then the rate of the fast pump is 1.5x.   (x+1.5x)*6 = 2.5x*6 = 15x, which is the capacity of the whole pool.   Working alone:   1.5x*Time 2.5 *6= 
<gadget id="calculator">2.5 *6</gadget>
<output>15</output>
15x, which is the capacity of the whole pool.   Working alone:   1.5x*Time= 15x   Time = 15/1.5= 
<gadget id="calculator">15/1.5</gadget>
<output>10</output>
10 hours   The answer is 10.
<result>D</result>
Two water pumps, working simultaneously at their respective constant rates, took exactly 6 hours to fill a swimming pool. If the constant rate of one pump was 1.5 times the constant rate of the other, how many hours would it have taken the faster pump to fill the pool if it had worked alone at its constant rate?