Question

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 hrs 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 1

Answer: C.  6

Step-by-step explanation:

Given : Time taken by Machine R to do the job = 36 hours

Time taken by Machine S to do the job = 18 hours

Let x be the number of each type of machine to do the job.

Then , according to the question the required equation will be :-

$\dfrac{x}{36}+\dfrac{x}{18}=\dfrac{1}{2}\\\\\Rightarrow\ x(\dfrac{1}{36}+\dfrac{1}{18})=\dfrac{1}{2}\\\\\Rightarrow\ \dfrac{x}{12}=\dfrac{1}{2}\\\\\Rightarrow\ x=\dfrac{12}{2}=6$

Hence, the number of machines of type R were used =6