<PRE><B>Question 640453</B>
Two pumps working together can fill a water tank in 18 minutes. one pump works twice as fast as the other pump. If each pump worked alone, how long would it take to fill the water tank?
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let x=minutes faster pump can fill tank by itself
Its work rate=1/x
2x=minutes slower pump can fill tank by itself
Its work rate=1/2x
1/18=work rate pumps working together
..
sum of individual work rates=work rate when working together
1/x+1/2x=1/18
LCD=2x
2+1=2x/18
3=x/9
x=27
2x=54
minutes faster pump can fill tank by itself=27
minutes slower pump can fill tank by itself=54</PRE>