SOLUTION: a pump can empty a small pond in 5hr. another more efficient pump can do the job in 3hr. how long would it take to empty the pond if both pumps were used?

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Question 887483: a pump can empty a small pond in 5hr. another more efficient pump can do the job in 3hr. how long would it take to empty the pond if both pumps were used?
Found 3 solutions by josgarithmetic, MathTherapy, Alan3354:
Answer by josgarithmetic(39617)   (Show Source):
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This combination of rates is simple addition. One job is "empty the pond".
is the combined rate in JOBS per HOUR.

Answer by MathTherapy(10552)   (Show Source):
You can put this solution on YOUR website!

a pump can empty a small pond in 5hr. another more efficient pump can do the job in 3hr. how long would it take to empty the pond if both pumps were used?

, or hours.
You can do the check!!
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Answer by Alan3354(69443)   (Show Source):
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a pump can empty a small pond in 5hr. another more efficient pump can do the job in 3hr. how long would it take to empty the pond if both pumps were used?
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The 1st pump does 1/5 of the pond per hour.
The 2nd pump does 1/3 of the pond per hour.
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Together, they do 1/5 + 1/3 of the pond per hour, = 8/15 of the pond/hour.
--> 15/8 hours/pond