SOLUTION: One pipe can fill a tank in 15 minutes. The tank can be drained by another pipe in 45 minutes. If both pipes are opened, how long will it take to fill the tank?

Algebra ->  Rate-of-work-word-problems -> SOLUTION: One pipe can fill a tank in 15 minutes. The tank can be drained by another pipe in 45 minutes. If both pipes are opened, how long will it take to fill the tank?      Log On


   

Question 921387: One pipe can fill a tank in 15 minutes. The tank can be drained by another pipe in 45 minutes. If both pipes are opened, how long will it take to fill the tank?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Rate of filling:
+1%2F15+ tanks / min
Rate of draining:
+1%2F45+
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Let +t+ = time in min to fill tank
+1%2F15+-+1%2F45+=+1%2Ft+
Multiply both sides by +45t+
+3t+-+t+=+45+
+2t+=+45+
+t+=+22.5+
It takes 22.5 min to fill tank
and
+.5%2A60+=+30+
It takes 22 min 30 sec to fill tank