SOLUTION: A pool can be filled by pipe A in 3 hours and by pipe B in 5 hours. When the pool is full, it can be drained by pipe C in 4 hours. If the pool is initially empty and all three pipe

Algebra ->  Rate-of-work-word-problems -> SOLUTION: A pool can be filled by pipe A in 3 hours and by pipe B in 5 hours. When the pool is full, it can be drained by pipe C in 4 hours. If the pool is initially empty and all three pipe      Log On


   

Question 920101: A pool can be filled by pipe A in 3 hours and by pipe B in 5 hours. When the pool is full, it can be drained by pipe C in 4 hours. If the pool is initially empty and all three pipes are open, write an equation to find how long it takes to fill the pool.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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A pool can be filled by pipe A in 3 hours and by pipe B in 5 hours.
When the pool is full, it can be drained by pipe C in 4 hours.
If the pool is initially empty and all three pipes are open,
write an equation to find how long it takes to fill the pool.
:
Let t = time required to fill the pool with all valves open
Let the completed job = 1 (a full pool)
Fill is +, drain is -
:
t%2F3 + t%2F5 - t%2F4 = 1
multiply equation by 60 to cancel the denominators, find t