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

Algebra ->  Customizable Word Problem Solvers  -> Misc -> 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      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


   



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) About Me  (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
:
%28%286-t%29%29%2F10 + 6%2F15 + 6%2F20 = 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
%28%286-3%29%29%2F10 + 6%2F15 + 6%2F20 = 1