Marge has 3 pumps for filling her swimming pool. When all 3 pumps work at their maximum rates, the swimming pool is filled in 60 minutes. Pump 1's maximum rate is twice the maximum rate of pump 2 and four times the maximum rate of pump 3. How long would it take Marge to fill the pool if she used only pump 3 at its maximum rate ? Options:
A) 2hrs, 48mins
B) 7hrs,
C) 7hrs, 12mins
D) 13hrs, 4mins
E) 14hrs, 24mins
The rate of pump 1 = 4x job/minute.   The rate of pump 2 = 2x job/minute.   The rate of pump 3 = x job/minute.   Given that x+2x+4x=1/60 --&gt; x=1/420--&gt; (time) = (reciprocal of rate) = 392 minutes = 7 hours   Answer: 7hrs,.
<result>B</result>
Marge has 3 pumps for filling her swimming pool. When all 3 pumps work at their maximum rates, the swimming pool is filled in 60 minutes. Pump 1's maximum rate is twice the maximum rate of pump 2 and four times the maximum rate of pump 3. How long would it take Marge to fill the pool if she used only pump 3 at its maximum rate ?