Question 177029
If Steven can mix 20 drinks in 5 minutes, Sue can mix 20 drinks in 10 minutes, and Jack can mix 20 drinks in 15 minutes, how much time does it take all 3 of them working together to mix 20 drinks/
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Steven rate = 20/5 = 4 drinks/min
Sue rate = 20/10 = 2 drinks/min
Jack rate = 20/15 = (1.333..)drinks/min
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Combined rate : (4+2+1.333) = (7.333..)drinks/min
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Time to mix 20 drinks: 
Convert to 20 drinks/x min
(20/7.333..)drinks / (20/7.333..)min = 20drinks/2.72 min
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Cheers,
Stan H.