BTGmoderatorLU wrote:Source: Economist GMAT Tutor

Working together, Joe and Joanne finish a job in 2 hours. How long will it take Jeremy and Joe to finish the job?

1) Working alone and without breaks, Joe takes 5 hours to finish the job, which is 400% as long as the time it takes Jeremy to finish the job.
2) Working alone and without breaks, Joanne takes 10 hours to finish 3 times the job.

The OA is A

To get a unique answer, we need to know the rates of Joe and Jeremey.

Let's take each statement one by one.

1) Working alone and without breaks, Joe takes 5 hours to finish the job, which is 400% as long as the time it takes Jeremy to finish the job.

Joe's rate = 5 hours for the job; thus,
Jeremy's rate = 5/400% = 1.25 hours for the job

We know both the rates. Sufficient.

2) Working alone and without breaks, Joanne takes 10 hours to finish 3 times the job.

From this, information, though we can get Joe's rate, we cannot get Jeremey's rate. Insufficient.

The correct answer: A

Hope this helps!

-Jay
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