SOLUTION: A pump can fill a swimming pool in 8 hours. Another lump can fill the same pool in 9 hours. How long will it take both pumps working together to fill the pool?

Question 829041: A pump can fill a swimming pool in 8 hours. Another lump can fill the same pool in 9 hours. How long will it take both pumps working together to fill the pool?
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
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rate pump 1:
r = 1/8
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rate pump 2:
r = 1/9
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rate pumps 1 & 2 together:
1/8 + 1/9
9/72 + 8/72
17/72
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time = 1/rate:
---
time pumps 1 & 2 together:
time = 1/r = 72/17
time = 4.235294117647059
---
answer:
time = 4 hours, 14 minutes, and 7.06 seconds
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