SOLUTION: A can do a certain work in 21 hrs. B can do the task in 28 hrs, C can do the task in 48 hrs. Find how long it will take to do the ask if all of three work

Algebra ->  Rate-of-work-word-problems -> SOLUTION: A can do a certain work in 21 hrs. B can do the task in 28 hrs, C can do the task in 48 hrs. Find how long it will take to do the ask if all of three work      Log On


   

Question 908534: A can do a certain work in 21 hrs. B can do the task in 28 hrs, C can do the task in 48 hrs. Find how long it will take to do the ask if all of three work
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Do it like this one.
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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?
1 solutions
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Answer 550883 by Alan3354(39871) on 2014-10-01 11:05:56 (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.