SOLUTION: It takes Printing machine A and B working together 2hrs 24min to complete a piece of job. both machines started working together and after 36min B broke down and A had to continue

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Question 894720: It takes Printing machine A and B working together 2hrs 24min to complete a piece of job. both machines started working together and after 36min B broke down and A had to continue alone. if it took 3hrs for machine A to complete the task , determine how long each machine would take to complete printin papers
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Each machine has a rate of printing expressed as:
( number of printing jobs finished ) / ( time to do all those jobs in hrs )
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Let +R%5Ba%5D+ = A's rate of printing
Let +R%5Bb%5D+ = B's rate of printing
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Note that +24+ min = +24%2F60+=+.4+ hrs
and +36+ min = +36%2F60+=+.6+ hrs
Given:
(1) +R%5Ba%5D+%2B+R%5Bb%5D+=+1+%2F+2.4+
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In +36+ minutes, how much of the job did
the machines finish working together?
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In +2.4+ hrs, they would have done the whole job
They finished +.6+%2F+2.4+=+1%2F4+ of the job in +36+ min
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There is +3%2F4+ of the job left to do
It took +3+ hrs for A to finish the job alone, so
A's rate of printing is:
+R%5Ba%5D+=+%28+3%2F4%29+%2F+3+
+R%5Ba%5D+=+1%2F4+ jobs / hr
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Now I can say:
(1) +R%5Ba%5D+%2B+R%5Bb%5D+=+1+%2F+2.4+
(1) +1%2F4+%2B+R%5Bb%5D+=+1+%2F+2.4+
(1) +1%2F4+%2B+R%5Bb%5D+=+10%2F24+
(1) +6%2F24+%2B+R%5Bb%5D+=+10%2F24+
(1) +R%5Bb%5D+=+4%2F24+
(1) +R%5Bb%5D+=+1%2F6+ jobs/hr
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A would take 4 hrs to do the job alone
B would take 6 hrs to do the job alone
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check:
(1) +R%5Ba%5D+%2B+R%5Bb%5D+=+1+%2F+2.4+
(1) +1%2F4+%2B+1%2F6+=+1+%2F+2.4+
(1) +6%2F24+%2B+4%2F24+=+10%2F24+
(1) +10%2F24+=+10%2F24+
OK