SOLUTION: One inlet pipe can fill an empty pool in 4 hours, and a drain can empty the pool in 10 hours. How long will it take the pipe to fill the pool if the drain is left open? thanks :

Algebra ->  Rate-of-work-word-problems -> SOLUTION: One inlet pipe can fill an empty pool in 4 hours, and a drain can empty the pool in 10 hours. How long will it take the pipe to fill the pool if the drain is left open? thanks :      Log On


   

Question 302994: One inlet pipe can fill an empty pool in 4 hours, and a drain can empty the pool in 10 hours. How long will it take the pipe to fill the pool if the drain is left open?
thanks :)
Found 2 solutions by stanbon, mananth:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
One inlet pipe can fill an empty pool in 4 hours, and a drain can empty the pool in 10 hours. How long will it take the pipe to fill the pool if the drain is left open?
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Filling rate: 1/4 pool/hr
Emptying rate: 1/10 pool/hr
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Together rate: 1/x pool/hr
==============================
Equation:
rate - rate = together rate
1/4 - 1/10 = 1/x
(10-4)/40 = 1/x
6/40 = 1/x
x = 40/6 = 20/2 = 6 2/3 hrs (time to fill the pool
==============================
cheers,
Stan H.

Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
One inlet pipe can fill an empty pool in 4 hours, and a drain can empty the pool in 10 hours. How long will it take the pipe to fill the pool if the drain is left open?

fills in 4 hours
it can do 1/4 of filling job in 1 hour
Drains in 10 hours
It can do 1/10 of draining job in 1 hour
the difference is the effective filling job done in 1 hour
1/4-1/10
5-2 /20
3/20 job in 1 hour
20 /3 hours it takes to fill when drain is open
6.66 hours
Ananth