SOLUTION: ONe person can wash 3 cars in 2 hours. Another can wash 3 cars in 1.5 hours. How long will it take them to wash the 3 cars together? 1/40+1/30=1/x 120/40+120/30=120/x 3+4=120

Algebra ->  Rate-of-work-word-problems -> SOLUTION: ONe person can wash 3 cars in 2 hours. Another can wash 3 cars in 1.5 hours. How long will it take them to wash the 3 cars together? 1/40+1/30=1/x 120/40+120/30=120/x 3+4=120      Log On


   

Question 173258: ONe person can wash 3 cars in 2 hours. Another can wash 3 cars in 1.5 hours. How long will it take them to wash the 3 cars together?
1/40+1/30=1/x
120/40+120/30=120/x
3+4=120/x
7x=120
x=17.14 for one car
52.42 minutes for 3 cars
Found 2 solutions by vleith, Alan3354:
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
Looks good to me

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
x=17.14 for one car
52.42 minutes for 3 cars
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3 x 17.14 = 51.42 minutes
OK otherwise.
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There's a shortcut you can use for 2 elements, the product over the sum:
2*1.5/(2+1.5) = 3/3.5 hours
= 360/7 minutes
= 51.42 minutes for 3 cars.