<PRE><B>Question 156116</B>
Steven can mix 20 drinks in 5 minutes,then he mix 4 drinks in a minute 
Sue can mix 20 drinks in 10 minutes,then he mix 2 drinks in a minute 
Jack can mix 20 drinks in 15 minutes, then he mix 4/3 drinks in a minute 

then in a minute working together they mix 4+2+4/3 drinks =22/3 drinks 
then 22/3 = 1 minute
     20  =  x minutes

x=20/(22/3)=60/22=30/11


Answer: 30/11 minutes (aprox 2.73 minutes)

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