SOLUTION: rowena can paint a car in 5 hours. Rudolf can paint the same car in 8 hours. they painted the car together for two hours and then rudolf quit to paint another car. how long will it

Algebra ->  Customizable Word Problem Solvers  -> Finance -> SOLUTION: rowena can paint a car in 5 hours. Rudolf can paint the same car in 8 hours. they painted the car together for two hours and then rudolf quit to paint another car. how long will it      Log On

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Question 842505: rowena can paint a car in 5 hours. Rudolf can paint the same car in 8 hours. they painted the car together for two hours and then rudolf quit to paint another car. how long will it take rowena to finish the job?
Answer by josgarithmetic(39625) About Me  (Show Source):
You can put this solution on YOUR website!
Rowena, 1/5 car per hour
Rudolf, 1/8 car per hour

Let t = unknown time that rowena paints the car alone

highlight_green%28%281%2F5%2B1%2F8%292%2B%281%2F5%29t=1%29, the completion of one whole job of "paint the car". Solve for t.

Multiplying both sides by 40 clears the denominators.
%288%2B5%292%2B8t=40
13%2A2%2B8t=40
8t%2B26=40
4t%2B13=20
4t=7
t=7%2F4
highlight%28t=1%263%2F4%29 hours.