SOLUTION: 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

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Question 192007This question is from textbook Elementary and intermediate algebra
: 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? This question is from textbook Elementary and intermediate algebra

Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
1 / (1/30 - 1/45) = 90 minutes
Let me explain,
If the full tank can be emptied in 30 minutes then 1/30 of the tank can be emptied in a minute.
If the empty tank can be filled in 45 minutes then 1/45 of the tank can be filled in a minute.
When the two pipes are open together then 1/30 - 1/45 = 1/90 of the tank is emtied in a minute.
Therefore it takes 90 minutes for the full tank to be emptied when the two pipes are open at the same time.