SOLUTION: It takes you 15 minutes to wash a car and it takes a friend in 9 minutes to wash a car how long does it take the two of you to wash 8 cars if you work together

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Question 897896: It takes you 15 minutes to wash a car and it takes a friend in 9 minutes to wash a car how long does it take the two of you to wash 8 cars if you work together
Found 2 solutions by ewatrrr, richwmiller:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
1%2F15+%2B+1%2F9+=+1%2Fx |Multiplying thru by 45x so as all denominators = 1
3x + 5x = 45
x = 45/8 (one car together), 8 cars... 45miin

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
a=15
b=9
1/a+1/b=1/x
1/15+1/9=1/x
1/15+1/9=1/5.625
1/x=1/5.625
x=5.625 per car together
8*5.625=45 minutes for them to wash 8 cars together