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 55 hrs and a machine of type S does the same job in 22 hours. If the company used the same number of each type of machine to do the job in 5 hours, how many machines of type R were used?  Choose one:
A) 22/7 B) 28/7 C) 23/7 D) 25/7 E) 22/7
Rate of machine R =1/55   Rate of machine S =1/22   since same no of machines used for R and S to do the same work in 5 hrs   So collective rate needed to finish the work in 5 hrs= 1/5   Let the no of machine be x   So, x/55 +x/22 =1/5   7x=22   x=22/7   So no of machine R is 22/7   Answer 22/7
<result>E</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 55 hrs and a machine of type S does the same job in 22 hours. If the company used the same number of each type of machine to do the job in 5 hours, how many machines of type R were used?