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by ssy » Sat Oct 27, 2007 5:52 am
A company has two types of machines, R and S. Operating at a constant rate, R does a job in 36 hours, S does the same job in 18 hours. If the company used the same number of each machine type to do a job in 2 hours, how many of type R were used?

3
4
6
9
12

6
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by Suyog » Sat Oct 27, 2007 6:08 am
R does a job in 36 hours = 1 /36
S does a job in 18 hours = 1 /18

Both together:

A + B = 1/36 + 1/18 = 1/12

Both machines complete the job in 12 hrs
Since the same number of m/c's are used.
If the job has to be completed in 2 hrs then 12 / 2 i.e.
6 machines will be reqd of each type.

Ans C.
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