Aplications of Rational Expressions

Question

One copy machine can run off copies in 15 minutes. A newer machine can do the same job in 10 minutes. How long would it take the two machines, working together, to make all the necessary copies?

Answer 1

Let x = amount of time that it takes to do the job if both machines are working together

 

Each minute, the first machine does 1/15 of the job and the second does 1/10 of the job

 

So, 1/15 + 1/10 = 1/x

 

Multiply the equation by the LCD, 30x, to obtain:

 

2x + 3x = 30

 

       5x = 30

 

        x = 6 minutes

 

 

Answer 2

This problem can be attempted with the concept of both probability and General Aptitude.

 

The answer for this question is 6 minutes. Please contact me for the detailed explanation