SOLUTION: A certain tank can be filled by pipe A in 12 minutes. Pipe B can empty the tank in 18 minutes. If both pipes are open, how long will it take to fill or empty the tank?

Algebra ->  Rate-of-work-word-problems -> SOLUTION: A certain tank can be filled by pipe A in 12 minutes. Pipe B can empty the tank in 18 minutes. If both pipes are open, how long will it take to fill or empty the tank?      Log On


   



Question 522778: A certain tank can be filled by pipe A in 12 minutes. Pipe B can empty the tank in 18 minutes. If both pipes are open, how long will it take to fill or empty the tank?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A certain tank can be filled by pipe A in 12 minutes. Pipe B can empty the tank in 18 minutes.
If both pipes are open, how long will it take to fill or empty the tank?
:
It takes less time to fill it than to empty it, therefore with both valves open the tank will be filled eventually
:
Let t = time to fill the tank with both valves open
Let a full tank = 1
t%2F12 - t%2F18 = 1
multiply by 36
36*t%2F12 - 36*t%2F18 = 36(1)
Cancel the denominators, results
3t - 2t = 36
t = 36 hrs to fill the tank with both valves left open