SOLUTION: Steve 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 long for all 3 working together to mix the 20 drinks?

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Question 321135: Steve 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 long for all 3 working together to mix the 20 drinks?
Found 2 solutions by solver91311, ehollins1:
Answer by solver91311(24713) (Show Source):
You can put this solution on YOUR website!

If A can do a job in x time periods, then A can do of the job in 1 time period. Likewise, if B can do the same job in y time periods, then B can do of the job in 1 time period. And for this problem, C can do the job in z time periods, so C can do of the job in 1 time period.

So, working together, they can do

of the job in 1 time period.

Therefore, they can do the whole job in:

time periods.

Hint: Consider mixing 20 drinks as 1 job.

John

Answer by ehollins1(8) (Show Source):
You can put this solution on YOUR website!
20 drinks in 5min equals 4 drinks per minute
20 drinks in 10min equals 2 drinks per minute
20 drinks in 15min equals 1.5 drinks per minute
for a total of 7.5 drinks per minute.
7.5*3min = 22.5 drinks
7.5*2min = 15 drinks
it takes 2.6667min to make 20 drinks with all three working
=(20/5)+(20/10)+(20/15)
=4+2+1.5
=7.5 (total amount of drinks dun per minute for all three bar tenders.)
20=7.5*x
20/7.5=(7.5/75.)x
2.667min=x
check solution:
2.6667*7.5 = 20.00025