Question 614712
If Steve can mix 20 drinks in 5 minuets, Sue can mix 20 drinks in 10 minuets, and Jack can mix 20 drinks in 15 minuets, how much time will it take all 3 of them working together to mix 20 drinks??
:
Since they are all doing the same job, mixing of 20 drinks, we can call the completed job 1
:
Each will do a fraction of the job, the three fractions will add up to 1
:
{{{t/5}}} + {{{t/10}}} + {{{t/15}}} = 1
multiply by 30 to clear the denominators
30*{{{t/5}}} + 30*{{{t/10}}} + 30*{{{t/15}}} = 30
cancel the denominators
6t + 3t + 2t = 30
11t = 30
t = {{{30/11}}}, about 2.73 minutes or 2 min 43.6 sec