SOLUTION: A pipe can fill a tank in 30 minutes. A second pipe can fill the same tank in 20 minutes. A drain can empty the tank in 15 minutes. If you left the drain open, how long will it t

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: A pipe can fill a tank in 30 minutes. A second pipe can fill the same tank in 20 minutes. A drain can empty the tank in 15 minutes. If you left the drain open, how long will it t      Log On

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Question 915624: A pipe can fill a tank in 30 minutes. A second pipe can fill the same tank in 20 minutes. A drain can empty the tank in 15 minutes. If you left the drain open, how long will it take to fill the tank with both pipes open?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add the rates of filling and subtract
the rate of draining
+1%2F30+%2B+1%2F20+-+1%2F15+=+1%2Ft+
Multiply both sides by +60t+
+2t+%2B+3t+-+4t+=+60+
+t+=+60+
It will take 1 hour with both filling pipes
open and the drain open