IR Explained: Q29: Baby Measurements

August 15, 2012

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This post is part of a series--IR Explained--that walks through the sample Integrated Reasoning questions provided in the latest edition of the GMAT Official Guide.

The graph in this Graphics Interpretation question shows the length and weight of 19 babies. The length is on the x-axis, and the weight is on the y-axis. The babies are broken down into two groups, A and B, with Group A babies shown as blue dots and Group B babies shown as triangles.

The first question, 29A, asks about the correlation between the length and weight of the babies. As shown in the graph, the longer babies tend to be heavier, and the shorter babies tend to be lighter. That is a strongly positive correlation.

For 29B, remember that probability is calculated as "desired outcomes" divided by "possible outcomes." Counting dots on the graph, observe that 10 babies weigh less than 3.5 kg--those are "possible outcomes." Of those 10, four ("desired outcomes") are Group A. The probability is 4/10, or 0.40.

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About the author: Jeff Sackmann has written many GMAT preparation books, including the popular Total GMAT Math, Total GMAT Verbal, and GMAT 111. He has also created explanations for problems in The Official Guide, as well as 1,800 practice GMAT math questions.

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