SOLUTION: Two pipes can empty pool in 3 hours. If the smaller pipe can empty it in 10 hours alone, how long can a larger pipe empty the pool alone?

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Question 1111965: Two pipes can empty pool in 3 hours. If the smaller pipe can empty it in 10 hours alone, how long can a larger pipe empty the pool alone?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +t+ = time in hrs for the larger pipe
to empty the pool
Rate of emptying for smaller pipe:
[ 1 pool emptied ] / [ 10 hrs ]
Rate of emptying for smaller pipe:
[ 1 pool emptied ] / [ t hrs ]
Add the rates of emptying to get the rate
with both pipes together
-------------------------------------------
+1%2F10+%2B+1%2Ft+=+1%2F3+
+1%2Ft+=+10%2F30+-+3%2F30+
+1%2Ft+=+7%2F30+
Multiply both sides by +30t+
+30+=+7t+
+t+=+4.2857+ hrs
The larger pipe alone takes 4.2857 hrs
-----------------------------------
check:
+1%2F10+%2B+1%2F4.2857+=+1%2F3+
+.1+%2B+.2333+=+.333+
+.333+=+.333+
OK