Math CentralQuandaries & Queries


Question from saurabh, a student:

At certain swimming pool certain pipes can fill it in 2 hours, another can fill it in 5 hours,and third pipe can empty the pool in 6 hours. with all three pipes turned on at the same time and starting with an empty pool , how long will it take to fill the pool


I'm not going to do this one for you, I will show you how to
do it. Instead of rating the pipes in hours-per-poolful, which don't add, rate them in poolfuls per hour, which do. So the first pipe yields 1/2 poolful per hour and so on.

Then when you've found the poolfuls per hour from all three pipes convert back. You can also use this if there are drains, that _lose_ soem number of poolfuls per hour.

Good Hunting!

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