SOLUTION: An inlet pipe can fill a pool in 12 hours, and the outlet pipe can empty it in 8 hours. If the pool is full and both pipes are open, how long will it take to empty?

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Question 1056547: An inlet pipe can fill a pool in 12 hours, and the outlet pipe can empty it in 8 hours. If the pool is full and both pipes are open, how long will it take to empty?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Rate of filling:
[ 1 pool filled ] / [ 12 hrs ]
Rate of emptying:
[ 1 pool emptied ] / [ 8 hrs ]
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The rate of emptying is faster than the
rate of filling, so with both pipes open,
the pool will not fill -it will empty.
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Add the positive rate and the negative rate
to get the rate of emptying. Let +t+ =
the time in hrs for the pool to empty
+1%2F12+-+1%2F8+=+-1%2Ft+
+2%2F24+-+3%2F24+=+-1%2Ft+
+-1%2F24+=+-1%2Ft+
+t+=+24+ hrs
The pool will empty in 24 hrs