Jun 22 2017

2018 GMAT Quant Official Guide – Detailed Analysis / Question Categorization

2018 GMAT Quant Official GuideGMAT Genius has thoroughly analyzed the 2018 GMAT Quant Official Guide and we want to share our insights with you. Feel free to read our detailed analysis of the 2018 GMAT Quant Official Guide or skip down to our conclusions. Wishing you tremendous success with the GMAT!

Overview of 2018 GMAT Quant Official Guide

The Official Guides for GMAT Review contain retired real GMAT questions, and are an essential component of your GMAT preparations. The GMAC places questions in order of increasing difficulty, based on its assessment of difficulty. The 2018 GMAT Quant Official Guide has no overlap with questions in the main Official Guide.

The 2018 GMAT Quant Official Guide contains 45 new questions out of the 300 total questions, representing 15% new content. These are new questions that we have not encountered before; they are not questions recycled from older GMAC resources.
 

Problem Solving

The 2018 GMAT Quant Official Guide contains 176 Problem Solving questions. The GMAC classifies question difficulty into three categories as follows:

Difficulty Number Percent Change
Easy 89 51% +4
Medium 43 24% (9)
Hard 44 25% +5

The Problem Solving section contains 26 new questions, with difficulty of Easy / Medium / Hard as follows: 15 / 5 / 6. This is in lieu of 26 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 11 / 14 / 1. Unlike in prior years, the GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment skews slightly more towards the center, but contains notable differences from the GMAC’s assessment. Our difficulty assessment is only 76.1% correlated with the GMAC’s assessment, demonstrating tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown:

Difficulty Number Percent Change
Super Easy 21 12% (1)
Easy 55 31%
Medium 62 35% (1)
Hard 30 17% +1
Very Hard 8 5% +1

Although math questions often entail multiple math concepts, GMAT Genius classifies questions based on our assessment of the primary math concept. We break down the 176 Problem Solving questions as follows:

Type Concept Number Percent Change
Arithmetic Basic 16 9.1% +2
Arithmetic Absolute Value 3 1.7%
Arithmetic Divisibility/Factors/Mult. 7 4% (3)
Arithmetic Exponents & Roots 8 4.5% (1)
Arithmetic Fractions & Ratios 22 12.5% +1
Arithmetic Percents 12 6.8% (3)
Arithmetic Pos/Neg & Odd/Even 1 0.6% (2)
Algebra Inequalities 4 2.3% +1
Algebra Linear Equations 9 5.1%
Algebra Quadratics 10 5.7% +2
Algebra Simultaneous Equations 6 3.4%
Algebra Variables in Answers 5 2.8% +1
Geometry Circles 4 2.3%
Geometry Coordinate 5 2.8%
Geometry Rectangles 5 2.8%
Geometry Triangles 4 2.3%
Geometry Other 4 2.3%
Statistics Averages 14 8% +1
Statistics Other 3 1.7%
Word Problems Combinatorics 4 2.3%
Word Problems Functions & Sequences 12 6.8%
Word Problems Groups/Sets 3 1.7% +1
Word Problems Probability 2 1.1%
Word Problems Revenue/Profit/Interest 5 2.8% +1
Word Problems Rate & Work 8 4.5% (1)

Here’s a list of the 26 new Problem Solving questions:
13, 22, 29, 31, 52, 55, 65, 70, 71, 73, 74, 75, 78, 85, 89, 92, 99, 102, 104, 117, 135, 141, 144, 156, 165, 168

Here’s a list of the 176 Problem Solving questions categorized by primary math concept:

Type Concept Question #s
Arithmetic Basic 2, 5, 21, 44, 45, 67, 75, 77, 85, 88, 89, 92, 94, 100, 162, 170
Arithmetic Absolute Value 95, 105, 150
Arithmetic Divisibility/Factors/Mult. 52, 86, 103, 114, 122, 171, 173
Arithmetic Exponents & Roots 34, 36, 38, 48, 90, 112, 143, 160
Arithmetic Fractions & Ratios 8, 20, 24, 35, 40, 43, 46, 49, 54, 55, 60, 64, 73, 74, 78, 83, 84, 91, 108, 136, 144, 176
Arithmetic Percents 7, 17, 28, 30, 47, 59, 99, 111, 117, 118, 132, 168
Arithmetic Pos/Neg & Odd/Even 14
Algebra Inequalities 4, 29, 101, 163
Algebra Linear Equations 3, 9, 13, 15, 18, 42, 50, 71, 98
Algebra Quadratics 1, 19, 22, 33, 63, 66, 110, 121, 128, 156
Algebra Simultaneous Equations 12, 25, 31, 32, 41, 133
Algebra Variables in Answers 16, 39, 102, 120, 125
Geometry Circles 37, 134, 151, 169
Geometry Coordinate 26, 87, 96, 109, 115
Geometry Rectangles 11, 27, 104, 129, 175
Geometry Triangles 62, 68, 140, 164
Geometry Other 23, 139, 146, 149
Statistics Averages 10, 58, 61, 82, 93, 107, 119, 126, 131, 135, 147, 148, 153, 161
Statistics Other 72, 79, 81
Word Problems Combinatorics 152, 154, 155, 157
Word Problems Functions & Sequences 53, 56, 69, 76, 80, 116, 127, 137, 138, 145, 159, 166
Word Problems Groups/Sets 106, 141, 142
Word Problems Probability 158, 167
Word Problems Revenue/Profit/Interest 6, 65, 124, 165, 172
Word Problems Rate & Work 51, 57, 70, 97, 113, 123, 130, 174

Data Sufficiency

The 2018 GMAT Quant Official Guide contains 124 Data Sufficiency questions. The GMAC classifies question difficulty into three categories as follows:

Difficulty Number Percent Change
Easy 27 22% +1
Medium 33 27% +2
Hard 64 52% (3)

In the Data Sufficiency section, questions are not fully presented in order of progressive difficulty, contrary to what the back cover of the book claims. Based on difficulty levels provided in the online version, Medium and Hard difficulty questions are interspersed. The following table shows the question numbers for each difficulty level:

Difficulty Question #s
Easy 177-203
Medium 204-235, 239
Hard 236-238, 240-300

The Data Sufficiency section contains 19 new questions, with difficulty of Easy / Medium / Hard as follows: 2 / 6 / 11. This is in lieu of 19 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 1 / 4 / 14. The GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment skews significantly easier, and contains notable differences from the GMAC’s assessment. Our difficulty assessment is only 68.5% correlated with the GMAC’s assessment, demonstrating tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown:

Difficulty Number Percent Change
Super Easy 12 10% +1
Easy 25 20% (3)
Medium 54 44%
Hard 27 22% +2
Very Hard 6 5%

Although many math questions entail multiple math concepts, GMAT Genius classifies questions based on our assessment of the primary math concept. We break down the 124 Data Sufficiency questions as follows:

Type Concept Number Percent Change
Arithmetic Basic 3 2.4% (2)
Arithmetic Absolute Value 1 0.8%
Arithmetic Divisibility/Factors/Mult. 8 6.5% +2
Arithmetic Exponents & Roots 12 9.7% (1)
Arithmetic Fractions & Ratios 8 6.5%
Arithmetic Percents 6 4.8%
Arithmetic Pos/Neg & Odd/Even 5 4%
Arithmetic Primes 3 2.4% +1
Algebra Inequalities 12 9.7% +2
Algebra Linear Equations 3 2.4%
Algebra Quadratics 7 5.6% +2
Algebra Simultaneous Equations 9 7.3% (5)
Geometry Circles 6 4.8% +1
Geometry Coordinate 4 3.2%
Geometry Rectangles 3 2.4%
Geometry Triangles 3 2.4%
Geometry Other 2 1.6%
Statistics Averages 6 4.8%
Statistics Other 5 4%
Word Problems Functions & Sequences 7 5.6%
Word Problems Groups/Sets 4 3.2% +1
Word Problems Probability 1 0.8% (1)
Word Problems Revenue/Profit/Interest 2 1.6%
Word Problems Rate & Work 4 3.2%

Here’s a list of the 19 new Data Sufficiency questions:
178, 193, 215, 216, 224, 226, 231, 239, 244, 246, 247, 257, 270, 281, 283, 285, 291, 295, 296

Here’s a list of the 124 Data Sufficiency questions categorized by primary math concept:

Type Concept Question #s
Arithmetic Basic 177, 180, 234
Arithmetic Absolute Value 214
Arithmetic Divisibility/Factors/Mult. 221, 224, 238, 247, 257, 272, 296, 297
Arithmetic Exponents & Roots 184, 210, 226, 240, 251, 254, 267, 268, 271, 282, 285, 300
Arithmetic Fractions & Ratios 182, 190, 201, 204, 233, 243, 255, 295
Arithmetic Percents 193, 199, 208, 222, 253, 266
Arithmetic Pos/Neg & Odd/Even 189, 196, 198, 213, 237
Arithmetic Primes 219, 270, 281
Algebra Inequalities 181, 188, 192, 200, 206, 215, 227, 231, 249, 252, 263, 276
Algebra Linear Equations 195, 218, 250
Algebra Quadratics 232, 239, 259, 265, 273, 279, 283
Algebra Simultaneous Equations 178, 202, 203, 217, 223, 230, 242, 269, 284
Geometry Circles 209, 216, 236, 256, 258, 278
Geometry Coordinate 191, 260, 290, 299
Geometry Rectangles 179, 185, 248
Geometry Triangles 261, 275, 291
Geometry Other 205, 207
Statistics Averages 194, 211, 228, 241, 244, 245
Statistics Other 225, 229, 235, 262, 294
Word Problems Functions & Sequences 197, 220, 264, 277, 280, 286, 287
Word Problems Groups/Sets 246, 274, 288, 293
Word Problems Probability 292
Word Problems Revenue/Profit/Interest 183, 186
Word Problems Rate & Work 187, 212, 289, 298

Online Interface

2018 GMAT Quant Official Guide Online InterfaceThe 2018 GMAT Quant Official Guide includes an access code (see inside front cover) that provides 12-month usage of an online version of this Official Guide. The online practice interface is the same as it was previously, except that the onerous limit of 10 saved sessions has been increased to 25 saved sessions in Exam Mode plus 25 saved sessions in Practice Mode (which you should not use, as mentioned below). The 100 questions from the Diagnostic Test chapter of the main Official Guide, but that are not contained in this printed book, are available in a separate tab that works with Exam Mode functionality.

Since the GMAT is a computer-based test, we believe that it is advisable to work though the questions online. We strongly suggest that you use Exam Mode rather than Practice Mode, since we recommend that students practice using timed question sets that replicate test day conditions. The functionality of the online platform is good overall. You can choose practice sets by question type and difficulty level. Every question lists the corresponding book question number for easy cross-referencing.

Other Notes

The Official Guides are for practicing with real GMAT questions, not for learning the underlying concepts. The book contains a 40-page Math Review section that provides a very high-level overview of the math concepts tested on the GMAT. This math review will be highly inadequate except perhaps for the most advanced math students. We recommend that you use additional study materials to learn the math concepts.

Although all questions include answer explanations, many GMAT test takers are far from satisfied with these explanations. The explanations can be brief and hard-to-understand for non-advanced students. Furthermore, certain explanations are convoluted and overlook more efficient approaches.

Conclusions

The 2018 GMAT Quant Official Guide has three primary weaknesses, in our opinion:

  1. An insufficient amount of difficult practice questions, particularly based on GMAT Genius’ assessment of difficulty.
  2. Math answer explanations that are too often either brief or convoluted.
  3. In the Data Sufficiency section, questions are not fully presented in order of progressive difficulty, contrary to what the back cover of the book claims.

Despite these flaws, the 2018 GMAT Quant Official Guide is an essential source of GMAT practice. We believe that every GMAT aspirant must use this book (or the prior edition). For the best value, we recommend purchasing this book as part of the 2018 GMAT Official Guide Bundle. If you already have the 2017 edition of this book, however, the replacement of 45 questions is not sufficient to make this edition worth purchasing.