Marge has 3 pumps for filling her swimming pool. When all 3 pumps work at their maximum rates, the swimming pool is filled in 90 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 2 at its maximum rate ?
Choose the correct choice from the following answers:
A) 2hrs, 48mins	B) 5hrs, 15mins	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=1/90 --&gt; x=1/630 --&gt; (time) = (reciprocal of rate) = 630 minutes x/2 = 5 hours and 15 minutes.   Answer: 5hrs, 15mins.
<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 90 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 2 at its maximum rate ?