Machine R and machine S work at their respective constant rates. How much time does it take...

[AAPL]

Official Guide

Machine R and machine S work at their respective constant rates. How much time does it take machine R, working alone, to complete a certain job?

1. The amount of time that it takes machine S, working alone, to complete the job is 3/4 the amount of time that it takes machine R, working alone, to complete the job.
2. Machine R and machine S, working together, take 12 minutes to complete the job.

OA C

[Jay@ManhattanReview]

Official Guide

Machine R and machine S work at their respective constant rates. How much time does it take machine R, working alone, to complete a certain job?

1. The amount of time that it takes machine S, working alone, to complete the job is 3/4 the amount of time that it takes machine R, working alone, to complete the job.
2. Machine R and machine S, working together, take 12 minutes to complete the job.

OA C

Both statements standalone are insufficient; from Statement 1, though we have the relative values for times for machine R and S, we cannot get the absolute values. From Statement 2, we cannot get the individual values of times.

Let's combine them.

Say the time for Machine R is x minutes; thus, the time for Machine S = 3x/4 minutes

Thus, from Statement 2, we have

1/x + 1/(3x/4) = 1/12

=> x = 28 minutes. Sufficient.

The correct answer: C

Hope this helps!

-Jay
_________________
Manhattan Review GMAT Prep

Locations: Manhattan Review Chennai | Hyderabad | GRE Prep New Delhi | Tarnaka GRE Coaching | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.