SOLUTION: One printing machine workes twice as fast as another. When both machines are used, they can print a magazine in 3h. How many hours would each machine require to do the job alone?

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Question 133572: One printing machine workes twice as fast as another. When both machines are used, they can print a magazine in 3h. How many hours would each machine require to do the job alone?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of working
(1st machines rate) + (2nd machines rate) = (rate printing together)
Let the 1st machines rate = r
Let the 2nd machine have the faster rate, 2r
r+%2B+2r+=+1%2F3
The 1%2F3 means (1 magazine/3 hours) which is the rate printing
together
3r+=+1%2F3
r+=+1%2F9
So, the 1st machine can print 1 magazine in 9 hours
For the 2nd machine,
2r+=+2%2F9
This means (2 magazines/9 hours) or,
(1 magazine)/4.5 hours)
The 2nd machine can print 1 magazine in 4.5 hours
check answers:
r+%2B+2r+=+1%2F3
1%2F9+%2B+2%2A%281%2F9%29+=+1%2F3
3%2F9+=+1%2F3
1%2F3+=+1%2F3
OK