SOLUTION: One pump can drain a pool in 11 minutes. When a second pump is also used, the pool only takes 8 minutes to drain. How long would it take the second pump to drain the pool if it wer

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: One pump can drain a pool in 11 minutes. When a second pump is also used, the pool only takes 8 minutes to drain. How long would it take the second pump to drain the pool if it wer      Log On

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Question 572862: One pump can drain a pool in 11 minutes. When a second pump is also used, the pool only takes 8 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 josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +t+ = time in minutes for 2nd pump alone to drain pool
Add the rates of pumping of each pump to get
the rate of both pumping together
Rate of 1st pump:
+1%2F11+ ( 1 pool drained/ 11 min )
Rate of 2nd pump:
+1%2Ft+ ( 1 pool drained / t min )
---------------------------
+1%2F11+%2B+1%2Ft+=+1%2F8+
Multiply both sides by +88t+
+8t+%2B+88+=+11t+
+3t+=+88+
+t+=+29.333+
+.333%2A60+=+20+
the 2nd pump takes 29 min and 20 sec to drain pool by itself
check answer:
+1%2F11+%2B+1%2F29.333+=+1%2F8+
+.09091+%2B+.034091+=+.125+
+.125001+=+.125+
error due to rounding off