SOLUTION: There is a job. A company alone needs 10 hours to finish, B needs 15 hours, and C needs 20 hours. A,B, and C work together. in the process, A stopped for a few hours. It took a tot

Question 1163790: There is a job. A company alone needs 10 hours to finish, B needs 15 hours, and C needs 20 hours. A,B, and C work together. in the process, A stopped for a few hours. It took a total of 6 hours for them to finish. How many hours did A stop for?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
There is a job. A company alone needs 10 hours to finish, B needs 15 hours, and C needs 20 hours.
A,B, and C work together. in the process, A stopped for a few hours.
It took a total of 6 hours for them to finish.
How many hours did A stop for?
:
let t = time that A stopped
let the completed job = 1
:
+ + = 1
multiply eq by 60, cancel the denominators
6(6-t) + 4(6) + 3(6) = 60
36 - 6t + 24 + 18 = 60
-6t + 78 = 60
-6t = 60 - 78
-6t - -18
t = -18/-6
t = 3 hrs that A stopped
:
:
Check with your calc
+ + = 1
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