SOLUTION: It takes tom 15 minutes to wash a car. it takes only 10 minutes with jerry helping. how long should it take jerry to wash the car alone? thank you.

Question 470361: It takes tom 15 minutes to wash a car. it takes only 10 minutes with jerry helping. how long should it take jerry to wash the car alone?

thank you.
Found 2 solutions by htmentor, sofiyac:
Answer by htmentor(1343) (Show Source): You can put this solution on YOUR website!
It takes tom 15 minutes to wash a car. it takes only 10 minutes with jerry helping. how long should it take jerry to wash the car alone?
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Tom's rate = 1 car per 15 minutes
Working together, their combined rate = 1 car per 10 minutes
In equation form, this is:
1/15 + 1/j = 1/10
Where j = the time it would take Jerry to was the car alone
Collect like terms and solve for j:
1/j = 1/10 - 1/15 -> 1/j = 15/150 - 10/150 = 5/150 = 1/30
So j = 30 minutes

Answer by sofiyac(983) (Show Source): You can put this solution on YOUR website!

cross multiply

so it would take 30 minutes
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