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?

A. 3B. 4C. 6D. 9E. 12

Answer: C. 6

Therefore, 6 machine R was used.

Step-by-step explanation:

Given;

Time taken for machine R = 36 hours

Time taken for machine S = 18 hours

The fraction of work completed by machine R and S in 1 hour is;

R = 1/36

S = 1/18

Let n represent the number of each type of machine used to do the job.

Time taken for n machine R and S is 2 hours.

The fraction of job completed by n Machine R and S is;

n (R + S) = 1/2

Since R = 1/36 and S = 1/18

n (1/36 + 1/18) = 1/2

n = 1/2 / (1/36 + 1/18)

n = 6

Therefore, 6 machine R was used.