IR Explained: Q34: Territorial Populations

August 27, 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 bar graph in this Graphics Interpretation question represents the change in population of three territories: A, B, and C. The introductory paragraph gives us the additional information that Nation X (of which the three territories are a part) saw its population increase from 17,000,000 to 22,500,000 over the same 20-year time period.

Question 34A asks you to compare the increase in population of Nation X to that of Territory C. As we've seen, the Nation's increase is 22,500,000 - 17,000,000 = 5,500,000.

C's increase is from roughly 2,900,000 to 4,600,000, or about 1,700,000. The question asks what percent 1.7 million is of 5.5 million, or 1.7/5.5. Since 1.7 is one-third of 5.1 (17 is one-third of 51), 1.7 is a bit less than one-third of 5.5. Of the choices, the correct answer is clearly 30 percent.

34B asks for another percentage: the portion of the nation's 2010 population represented by the three territories shown in the graph.

The territories have populations of roughly 7,300,000, 5,600,000, and 4,600,000, for a total of 17,500,000. The nation's population is 22,500,000. Thus, the answer is 17,500,000/22,500,000, or 175/225.

You can simplify the fraction by dividing top and bottom by 25, for 7/9. That's about 78%, so the correct answer is between 70% and 80%.

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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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