IR Explained: Q28: Transaction Types

August 13, 2012

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.

This graph depicts eight transaction amounts, which we can group into four pairs. For instance, the grey bars depict debit card transactions; the graph shows that there were 39 million of them in 2006 and 24 million in 2009. The blue bar shows 24 million and 30 million for the same two years--that represents paper checks.

28A asks which type of transaction incresaed by 25% from 2006 to 2009. You don't even need to worry about the number. Of the four transaction types, only one increased at all! Debit card, credit card, and auto transfer transactions all decreased. Thus, the answer is paper check transactions, which increased by 24 to 30--sure enough, 25%.

28B requires more math. Notice that from 2006 to 2009, credit card transactions decreased from 22 to 20. (I've dropped "millions" to make the amounts simpler.) The question proposed that the total value of these transactions increased by 10%.

Say that each transaction in 2006 was $1, meaning that the 22 transactions had a total value of $22. If the total value increased by 10%, that's $2.2, for a 2009 total of $22 + $2.2 = $24.2. In 2009, there are only 20 transactions, so the value per transaction is $24.2/20 = $12.1/10 = $1.21.

Thus, the average value of each transaction increased from $1 to $1.21, or 21.0%.

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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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