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 24 hrs and a machine of type S does the same job in 12 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?
Choose the correct choice from the following answers
A) 3	B) 4	C) 6	D) 9	E) 12
Rate of machine R = 1/24   Rate of machine S = 1/12   Rate of R+S = 1/8   To finish the work in 2 hrs, the combined rate needs to be 1/2.   x * 1/8 = 1/2   x = 4   The answer is 4.
<result>B</result>
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 24 hrs and a machine of type S does the same job in 12 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?