Source: Official Guide Revised GRE 2nd Ed. Part 9; Section 5; #16


Jacob’s weekly take-home pay is n dollars

Jacob’s weekly take-home pay is n dollars. Each week he uses 4n/5 dollars for expenses and saves the rest. At those rates, how many weeks will it take Jacob to save $500, in terms of n? 500/n, 2,500/n, n/625, n/2,500, 625n

2 Explanations


Jay Villanueva Jr

What I did in a attempt to solve this question was set up the following equation:

500= n - (4n/5)
I than multiplied everything by 5 to get:
which solves to be
than I divided both sides by n, to get:
2500/n which is answer choice B

Is this a correct way to answer this question?

Aug 14, 2016 • Comment

Sam Kinsman, Magoosh Tutor

Hi Jay,

The equation that you've set up isn't one that get from the information that we're given. We don't know how much Jacob makes in terms of dollars (nor how much he saves in terms of dollars), so we can't set 500 equal to n - (4n/5).

As Chris explains in the video, the best way to solve this problem is by plugging numbers into the answer choices. If Jacob makes $5 a week, he saves $1 a week, so it will take him 500 weeks to save $500. So we can set each n equal to 5 in the answer choices, and see which answer choice gives us a result of 500.

Aug 19, 2016 • Reply


Gravatar Chris Lele, Magoosh Tutor

Dec 8, 2012 • Comment

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