SOLUTION: 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 will it take all 3 of them working together t

Question 331418: 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 will it take all 3 of them working together to mix the 20 drinks?
I started off by:
(x/5) + (x/10) + (x/15) = 1
Need a common denominator in order to add:
which is 30.
(6x/30) + (3x/30) + (2x/30) = 1
= (6x + 3x + 2x)/ 30
= 11x/ 30
= x = 30/11 = 2.72 which is 2 mintues and 7 seconds
However, the answer is not correct according to the solution. Am I missing a step? Or is the solution incorrect?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
But 2.72 min is not 2 min, 7 sec. It's: 2 + .72(60) = 2 min 43.2 sec
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