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one machine and another machine

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one machine and another machine

by yasem77 » Sun May 24, 2009 11:25 am
If it would take one machine 10 minutes to fill a large production order and another machine 12 minutes to fill the same order, how many minutes would it take both machines working together, at their respective rates, to fill the order?

a) 4 1/60
b) 5
c) 5 5/11
d) 5 1/2
e) 11

Can somebody help me? I don´t know how to get solution 5 5/11. I always get 5 1/2. Thanks:-)
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by Neo2000 » Sun May 24, 2009 12:38 pm
This is a Time and Work problem.

If a machine can do X amount of work in a minutes, then in 1minute it will do X/a amount of work.

For the given two machines, this will now come to 1/10 and 1/12
Which means that combined, in 1minute, the two machines will do 1/10 +1/12 amount of work

[spoiler]Therefore total amount of work done in 1minute = 22/120 = 11/60
To do 1 complete unit of work they will take 60/11 = 5 5/11minutes[/spoiler]
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