GMAT by the Numbers: Proportions

Now that you’ve learned how to approach proportions questions on the GMAT, let’s add one more dimension to your understanding of how they work.

Take a moment to try this question. Following is performance data from thousands of people who have studied with Kaplan over the decades. Through analyzing this data, we will show you how to approach questions like this one most effectively and how to avoid similarly tempting wrong answer choice types on Test Day.

  1. The price of a certain car this year is $42,000, which is 25 percent greater than the cost of the car last year. What was the price of the car last year?
    1. $27,000
    2. $28,000
    3. $31,500
    4. $33,600
    5. $34,500

Explanation

The test makers often set up percentage problems to reward those who do two important things. The first is to be careful about what number the percentage is applied to. The second is to remember to look for ways to simplify calculations.

This problem tells you that an increase of 25% raises the price of a car to $42,000. Be careful to apply that 25% increase to the unknown original price, not the $42,000. Decreasing $42,000 by 25% yields $31,500, which is the most common wrong answer. Avoid that one error, and your odds of getting the right answer go up dramatically.

If you set up the arithmetic the way the GMAT presents it, you get:

Original price × 1.25 = 42,000

This would have you dividing 42,000 by 1.25—a simple task for a calculator but a time-consuming one for a person. On the GMAT, you’ll often have more success by converting percentages to fractions. An increase of 25% means an increase of , bringing the total up to of the original:

Choice (D) is correct.

More GMAT by the Numbers . . .

To see more questions with answer choice statistics, be sure to review the full-length CATs in your online resources.