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 workimg together to

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Question 539754: 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 workimg together to mix the 20 drinks?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of mixing drinks to get
their rate working together
Call mixing 20 drinks ( 1 job )
Steven's rate is ( 1 job ) / ( 5 min )
Sue's rate is ( 1 job ) / ( 10 min )
Jack's rate is ( 1 job ) / (15 min )
Let +t+ = time for all 3 working
together to do 1 job
+1%2F5+%2B+1%2F10+%2B+1%2F15+=+1%2Ft+
Multiply both sides by +30t+
+6t+%2B+3t+%2B+2t+=+30+
+11t+=+30+
+t+=+2.73+
+.73%2A60+=+43.6+
It will take them 2 min and 44 sec