SOLUTION: One pump can drain a pool in 12 minutes. When a second pump is also used, the pool only takes 7 minutes to drain. How long would it take the second pump to drain the pool if it wer

Question 557265: One pump can drain a pool in 12 minutes. When a second pump is also used, the pool only takes 7 minutes to drain. How long would it take the second pump to drain the pool if it were the only pump in use?
Answer by bluemockingjay7(41) (Show Source): You can put this solution on YOUR website!
rate x time = work
pump A | 1/12 x 7 = 7/12
pump B | 1/x x 7 = 7/x
7/12 + 7/x = 1
LCM = 12x
12x(7/12 + 7/x = 1)
7x + 84 = 12x
84 = 12x - 7x
84 = 5x
84/5 = 5x/5
84/5 minutes or 16 4/5 minutes or 16 minutes and 48 seconds
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