Question 499335
9 large hoses fill the pool in 4 hrs.
Each hose does 1/9 of the job and takes 4 hours to do it.
So, each large hose can do 1/36 of the job per hr.
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6 small hoses fill the pool in 8 hrs.
Each hoses does 1/6 of the job and takes 8 hours to do it.
So, each small hose can do 1/48 of the job per hr.
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How long will it take 4 large and 8 small hoses to do the job?
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(4*(1/36) + 8*(1/48)) * t = 1 (the whole job)
(1/9 + 1/6)t = 1
15/54 t = 1
t = 54/15
t = 3 9/15 hr
9/15 hr = 36 min
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t = 3 hr 36 min