SOLUTION: Hope I'm in the right section!!!! This seems like a variation of an average problem. It is a very basic problem but for the life of me I can't find the equation to solve this pr

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Question 39220: Hope I'm in the right section!!!! This seems like a variation of an average problem. It is a very basic problem but for the life of me I can't find the equation to solve this problem ( even when I have the correct answer at hand )
Sam makes 20 drinks in 5 minutes , Sue makes 20 drinks in 10 minutes, and Jack makes 20 drinks in 15 minutes. If they work together how long will it take them to make 20 drinks????? ( answer listed as 2 min. 44 sec. ) what formula is used to solve this??
Answer by Nate(3500) (Show Source):
You can put this solution on YOUR website!
Rate ....
Sam: (1/5)
Sue: (1/10)
Jack: (1/15)
Time ....
t
R * T = Work
(t/5) + (t/10) + (t/15) = 1
3t + 1.5t + t = 15
5.5t = 15
t = (15/5.5) = (150/55) = 30/11 = about 2 min. and 44 sec.