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 44 hrs and a machine of type S does the same job in 20 hours. If the company used the same number of each type of machine to do the job in 4 hours, how many machines of type R were used?	Choose the correct answer.
A) 56/21 B) 59/16 C) 44/21 D) 55/16 E) 12/59
Rate of machine R =1/44   Rate of machine S =1/20   since same no of machines used for R and S to do the same work in 4 hrs   So collective rate needed to finish the work in 4 hrs= 1/4   Let the no of machine be x   So, x/44 +x/20 =1/4   (5x+11x)/220=1/4   16x=55   x=55/16   So no of machine R is 55/16   Answer 55/16
<result>D</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 44 hrs and a machine of type S does the same job in 20 hours. If the company used the same number of each type of machine to do the job in 4 hours, how many machines of type R were used?