SOLUTION: A new type of pump can drain a certain pool in 6 hours. An older pump can drain the pool in 14 hours. How long will it take both pumps working together to drain the pool ?

Question 1140553: A new type of pump can drain a certain pool in 6 hours. An older pump can drain the pool in 14 hours. How long will it take both pumps working together to drain the pool ?
Found 3 solutions by ikleyn, rothauserc, Alan3354:
Answer by ikleyn(52776)   (Show Source): You can put this solution on YOUR website!
.

The new pump drains of the pool volume per hour. The old pump drains of the pool volume per hour. Working together, the two pumps drain = = of the pool volume per hour. It means that the two pumps will drain the pool in hours = hours = 4.2 hours = 4 hours and 12 minutes. ANSWER

Solved.

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It is a standard and typical joint work problem.

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Answer by rothauserc(4718)   (Show Source): You can put this solution on YOUR website!
let t be the hours it takes both pumps working together to drain the pool
:
1/6 + (1/14) = (14 + 6)/84 = 20/84 = 10/42
:
working together, the pumps do 10/42 of the job in 1 hour
:
also working together they do 1/t per hour, then
:
10/42 = 1/t
:
invert the two fractions and solve for t
:
t = 42/10
:
t = 4.2
:
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working together, they empty the pool in 4.2 hours
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:

Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
6*14/(6+14) = 4.2 hours
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