SOLUTION: printing machine A can do printing in 8 hours. With the machine B the same printing would take 12 hours. It was decided that both machines will be used for the printing. However, a

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Question 905924: printing machine A can do printing in 8 hours. With the machine B the same printing would take 12 hours. It was decided that both machines will be used for the printing. However, after a while the machine A broke down. After that it took 6 hours to finish the printing with machine B. How many hours did the machine A print before it broke down?
Answer by josgarithmetic(39614) About Me  (Show Source):
You can put this solution on YOUR website!
RATES JOB/HOUR
Machine A, 1%2F8
Machine B, 1%2F12
CombinedAB, 1%2F8%2B1%2F12=3%2F24%2B2%2F24=5%2F24

RT=J Uniform Rate rule for doing a job

The job is split into two time quantities. The combined machines part for unknown t time and then the machine B part which was 6 hours.

highlight%28%285%2F24%29%2At%2B%281%2F12%29%2A6=1%29, doing ONE job.
%285%2F24%29t%2B%281%2F2%29=1
%285%2F24%29t=1%2F2
t=24%2F%285%2A2%29
t=12%2F5
highlight%28t=2%262%2F5%29
2 hours 24 minutes, time that A and B worked together before A quit.