SOLUTION: Filling a tank. A water tank has an inlet pipe and a drain pipe. A full tank can be emptied in 30 minutes if the drain is opened and an empty tank can be filled in 45 minutes wi

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Question 201089: Filling a tank. A water tank has an inlet pipe and a drain
pipe. A full tank can be emptied in 30 minutes if the drain
is opened and an empty tank can be filled in 45 minutes
with the inlet pipe opened. If both pipes are accidentally
opened when the tank is full, then how long will it take to
empty the tank?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let t = time in minutes to empty tank with
both pipes open
Given:
drain pipe rate:
(1 tankful)/(30 min)
inlet pipe rate:
(1 tankful)/(45 min)
1%2F30+-+1%2F45+=+1%2Ft
Multiply both sides by 90t
3t+-+2t+=+90
t+=+90
It will take 90 min to empty tank
with both pipes open.