SOLUTION: how do you set up this word problem? A pipe can fill a pool in 9 hours. if a second pipe is used, the pool can be filled in 3 hours. how long would it take the second pipe alon

Algebra ->  Rate-of-work-word-problems -> SOLUTION: how do you set up this word problem? A pipe can fill a pool in 9 hours. if a second pipe is used, the pool can be filled in 3 hours. how long would it take the second pipe alon      Log On


   

Question 859350: how do you set up this word problem?
A pipe can fill a pool in 9 hours. if a second pipe is used, the pool can be filled in 3 hours. how long would it take the second pipe alone to fill the pool.
Answer by josgarithmetic(39625) About Me  (Show Source):
You can put this solution on YOUR website!
The fill rates of pipes working at the same time are summed.

apipe, 1%2F9 pool/hour
apipe+secpipe, 1%2F3 pool/hour

Think about the additive nature of the rates. You want to find the fill rate for "secpipe". That is how I'm abbreviating the "second pipe".

apipe%2Bsecpipe=apipe%2Bsecpipe
Let's say the TIME for secpipe to fill the pool if working alone, is h.
highlight%281%2F9%2B1%2Fh=1%2F3%29;
Solve for h.
-
1%2Fh=1%2F3-1%2F9
1%2Fh=3%2F9-1%2F9
1%2Fh=2%2F9
Reciprocals are also equal...
highlight%28h=9%2F2%29 or highlight%28h=4%261%2F2%29 hours for Second Pipe alone to fill the tank.