Official Guide 12th Edition: Data Sufficiency
The 11th edition has 179 Data Sufficiency problems (including 24 Diagnostic problems). In the changeover to the 12th edition, 75 problems were removed, leaving 104 repeats (including all Diagnostics), and 94 problems were added, yielding 198 Data Sufficiency problems in the 12th edition.
Among the question formats, Data Sufficiency has the highest proportion of new problems (47%). This section also grew by 19 problems, much more than any other question format. (At the same time, Problem Solving decreased by 19 problems.) These changes could reflect an increased emphasis on this problem type.
The number of Word Translations questions (word problems of various types) has grown significantly, particularly among the Statistics and non-specific Algebraic Translations topics. Meanwhile, the number of pure Algebra problems (especially Inequalities and Basic Equations) has fallen substantially.
The GMAT has a number of different obstacles at its disposal to hide what information is needed to solve Data Sufficiency problems. This analysis suggests that the GMAT may be shifting towards word problems as the preferred Data Sufficiency obstacle. Furthermore, the GMAT may be shifting away from pure Algebra as the preferred obstacle.
However, we must caveat that you should not over-interpret this change. Some variation is to be expected. Also remember that you generally need pure Algebra skills to solve Word Translations problems. After you've translated the word problems into algebra, you must often use algebraic manipulation to complete the analysis.
This graph displays the difficulty level of problems that were removed, repeated, and added. Excluding problems in the Diagnostic exam, higher-numbered problems are more difficult, according to the GMAT. On the left, red problems were removed from the 11th edition. On the right, dark-green problems were added to the 12th edition. Light colors are repeats, as shown by a few correspondences in the middle.
In the Data Sufficiency section, primarily Easy and Medium-Hard problems were removed; however, problems of all difficulties were deleted. In some cases, groups of 4 or 5 problems were removed or preserved at a time. Additions were made at all levels of difficulty, but not quite as many at the highest end.
- Several of the new Word Translations problems require that you keep track of 3 or 4 variables. Sometimes, you are given variables (often with subscripts, such as p1 and p2). In other cases, you must name the variables yourself and/or keep track of them in a table.
- Many new problems impose constraints on variables. Often, variables are restricted to positive values explicitly (x > 0) or implicitly (x is the tax rate). A few problems impose an integer constraint as well (x is the number of cookies). As you solve for the variable – or, better, as you determine whether you can solve – remember to take these constraints into account. For instance, a quadratic equation may have two solutions, but if one solution is negative, it may be invalid. In this case, you would then have sufficiency, because only the positive solution is valid.
- Many new problems require manipulation of inequalities in some way, even though the number of problems classified as “Inequalities” has decreased. The GMAT may be shifting this topic to more of a word-problem format. In most of the new 12th edition problems, the variables turn out to be restricted to positive numbers (see the previous point). In fact, the GMAT has removed many inequality problems that required you to deal with both positive and negative cases in the same problem.
- Many new problems require statistics knowledge and skills. Topics such as weighted averages and medians continue to grow in importance.