A company has two types of machines, type R and type S. Operating at a constant rate, a machine of type R does a certain job in 36 hours and a machine of type S does the same job in 18 hours. If the company used the same number of each type of machine to do the job in 2 hours, how many machines of type R were used?
R does the job in 36 hours so in 1 hour R finishes 1/36 job
S does the job in 18 hours so in 1 hour S finishes 1/18 job
Both work togther for an hour then they can finish 1/18 (1+1/2) = 1/12 job
So both working together to finish 1 job will take 12 hours, but we need to finish the job in 2 hours that means we will 6 machine of each type.
My answer is 6
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