SOLUTION: a new photocopier works 4 times as fast as an old one. when the machines work together, a unicersity can produce all its staff manuals in 12 hr. find the time it would take each ma

Question 718810: a new photocopier works 4 times as fast as an old one. when the machines work together, a unicersity can produce all its staff manuals in 12 hr. find the time it would take each machine working alone to complete the job
Found 2 solutions by solver91311, josmiceli:
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

Let's say that it takes hours for the new machine to do the job by itself. Then it must take hours for the old machine by itself. Then we can say that the new machine can do of the job in one hour, and the old machine can do of the job in one hour. Since we know that it takes 12 hours for both machines working together, we know that the two machines working together can do of the job in one hour. All of that leads us to:

Solve for , then calculate

John

Egw to Beta kai to Sigma
My calculator said it, I believe it, that settles it

Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = the rate of old copier in ( copy job ) / ( hrs )
Let = the rate of the new copier
Add the rates to get the rate working together
( 1/12 means ( 1 copy job ) / ( 12 hrs ) )

and

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The old copier can complete the job in 60 hrs working alone
The new copier can complete the job in 15 hrs working alone

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