SOLUTION: If two people work at washing 5 cars and one can do all 5 cars on their own in 36 minutes and the other can do all 5 on their own in 42 minutes, how long does it take to wash all 5

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Question 1104645: If two people work at washing 5 cars and one can do all 5 cars on their own in 36 minutes and the other can do all 5 on their own in 42 minutes, how long does it take to wash all 5 working together?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
If two people work at washing 5 cars and one can do all 5 cars on their own in 36 minutes and the other can do all 5 on their own in 42 minutes, how long does it take to wash all 5 working together
:
let t = time required working together
let the completed job = 1 (the washing of 5 cars)
:
Each will do a fraction of the job; the two fractions add up to 1
t%2F36 + t%2F42 = 1
multiply by the least common multiplier;252, cancel the denominators
252*t%2F36 + 252*t%2F42 = 252
7t + 6t = 252
13t = 252
t = 252/13
t = 19.4 min working together
:
:
Check
19.4%2F36 + 19.4%2F42 =
.539 + .462 = 1.00