Guess What? Guessing Does Not Work Well On the IR

Written by Kelly Granson. Posted in GMAT Study Guide

article-new ehow_images_a02_3l_d5_do-threecup-shuffle-magic-trick-800x800Unfortunately, guessing is an important part of GMAT. Some guesses are educated, and have a good chance of being effective and some are entirely random. In this post we will discuss why random guessing on the Integrated Reasoning section does not really work well. On the way, we will also review some basics of probability :).

When you make a random guess on a Verbal or Quantitative question of the GMAT, your chance of getting it right is 1 in 5, or 20%, which is not that bad. On the IR section, problems usually have two or three parts, and you have to make all selections correctly to get credit for the problem; there is no partial credit. You may have a Two-Part Analysis problem like this:

If you run R mph and burn C calories per minute, in terms of R and C, how many calories are burned in H hours? How many hours should you run to burn B calories?

In the table below, make one selection in each column.

Calories burned in H hoursHours to burn B calories
22.08
60CH
60RC
22.081
22.082


where you have to select one option in each column. You have to make correct selections in both columns to get credit for the problem.

There are five options in the first column, so your chances to get the right answer there are 1/5.

There are five options in the second column, so your chances to get the right answer there are 1/5.

You know that the probability of both events happening is the product of their individual probabilities:

1/5 × 1/5 = 1/25 or 4%

That's not much of a chance. So yes, in some cases, you might have to make a low-probability guess like this, but you are well advised to manage your time so that it won't be necessary. Check out this post that deals specifically with time management on the IR section of the GMAT.

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