Question 1140971
 One hose can fill a small swimming pool and 65 minutes.  A larger  hose can fill a swimming pool in 35 minutes. How long will it take both hoses to fill the swimming pool?
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Assuming it's the same swimming pool:
65*35/(65+35) minutes
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It's a parallel work problem, been done 1000's of times on this site.
Look it up.