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?

Question

A. 2 minutes and 44 seconds
B. 2 minutes and 58 seconds
C. 3 minutes and 10 seconds
D. 3 minutes and 26 seconds
E. 4 minutes and 15 seconds

Answer 1

Stevenrate=20/5 or 4 drink/min
Suerate=20/10 or 2 drink/min
Jackrate=20/15 or 1.33 drink/min

So in one minute, they can combined mix 7.33 drinks.

drinks=combinedrate*time
20=7.33 t
solve for time.