SOLUTION: each of two brothers can wash a car in 1 hour ; however, their sister can wash the car in 45 minutes. if all three work together, how long will it take to wash the car?

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: each of two brothers can wash a car in 1 hour ; however, their sister can wash the car in 45 minutes. if all three work together, how long will it take to wash the car?      Log On


   

Question 908224: each of two brothers can wash a car in 1 hour ; however, their sister can wash the car in 45 minutes. if all three work together, how long will it take to wash the car?
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Each brother does 1/60 of the job per minute.
The sister does 1/45 per minute.
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Together, they do 1/60 + 1/60 + 1/45 per minute.
Add them, get job/minute
Invert that to get minutes/job.