Category: GMAT Math

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

Overview of 2018 GMAT Official Guide Bundle

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 three books in this bundle have no overlap in practice questions.

Our objective below is to provide a combined analysis of each question type (e.g. combine data for all Problem Solving questions across all books). You will find a list of new questions and detailed question categorization in our prior posts on the individual books:
The 2018 Official Guide for GMAT Review
The 2018 Official Guide for GMAT Quantitative Review
The 2018 Official Guide for GMAT Verbal Review

The 2018 GMAT Official Guide Bundle contains 220 new questions out of the 1,566 total questions (including Integrated Reasoning). Excluding the 100 questions in the Diagnostic Exam section of the main book, the new questions represent 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 Official Guide Bundle contains a total of 430 Problem Solving questions. The GMAC classifies question difficulty into three categories as follows:

There are 61 new Problem Solving questions, with difficulty of Easy / Medium / Hard as follows: 37 / 12 / 12. This is in lieu of 61 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 19 / 17 / 25.

GMAT Genius classifies question difficulty into five categories. Our assessment of Problem Solving skews noticeably less difficult / more towards the center and is only 72.1% correlated with the GMAC’s assessment, demonstrating tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown:

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 430 Problem Solving questions as follows:

Data Sufficiency

The 2018 GMAT Official Guide Bundle contains a total of 322 Data Sufficiency questions. The GMAC classifies question difficulty into three categories as follows:

There are 45 new Data Sufficiency questions, with difficulty of Easy / Medium / Hard as follows: 13 / 16 / 16. This is in lieu of 45 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 4 / 8 / 33.

GMAT Genius classifies question difficulty into five categories. Our assessment skews significantly easier and is only 61.0% correlated with the GMAC’s assessment. Here’s our breakdown:

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 322 Data Sufficiency questions as follows:

Sentence Correction

The 2018 GMAT Official Guide Bundle contains a total of 158 Sentence Correction questions. The GMAC classifies question difficulty into three categories as follows:

There are 38 new Sentence Correction questions, with difficulty of Easy / Medium / Hard as follows: 12 / 4 / 22. This is in lieu of 38 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 7 / 13 / 18. The GMAC has assigned a different difficulty rating to a total of 17 Sentence Correction questions, upgrading these 17 from Medium to Hard difficulty.

GMAT Genius classifies question difficulty into five categories. Our assessment skews noticeably easier and is only 59.9% correlated with the GMAC’s assessment, clearly demonstrating the subjectivity involved in assessing question difficulty. Here’s our breakdown:

Although Sentence Correction questions typically entail multiple grammar concepts (as described on our website), GMAT Genius classifies questions based on our assessment of the primary tested concept. We classify the 271 Sentence Correction questions as follows:

Critical Reasoning

The 2018 GMAT Official Guide Bundle contains a total of 224 Critical Reasoning questions. The GMAC classifies question difficulty into three categories as follows:

There are 31 new Critical Reasoning questions, with difficulty of Easy / Medium / Hard as follows: 7 / 7 / 17. This is in lieu of 31 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 10 / 8 / 13. The GMAC has assigned a different difficulty rating to one Critical Reasoning question.

GMAT Genius classifies question difficulty into five categories. Our assessment skews slightly more towards the center, yet is only 72.3% correlated with the GMAC’s assessment, clearly indicating subjectivity involved in assessing question difficulty. Here’s our breakdown:

We have grouped the questions based on the question type categorization that GMAT Genius uses for Critical Reasoning (as described on our website). We break down the 224 Critical Reasoning questions as follows:

Reading Comprehension

The 2018 GMAT Official Guide Bundle contains a total of 261 Reading Comprehension questions across 52 passages. The GMAC classifies question difficulty into three categories as follows:

There are 37 new Reading Comprehension questions, with difficulty of Easy / Medium / Hard as follows: 13 / 18 / 6. This is in lieu of 37 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 3 / 23 / 11. The GMAC has assigned a different difficulty rating to a total of 4 Reading Comprehension questions.

GMAT Genius classifies question difficulty into five categories. Whereas the GMAC assigns the same difficulty to all questions for a given passage (except in the Diagnostic Exam section), GMAT Genius assesses the difficulty of each question individually. Our assessment skews very slightly harder, but is only 58.8% correlated with the GMAC’s assessment, in large part due to different difficulty assessment methodologies. Here’s our breakdown:

We have grouped the questions based on the question type categorization that GMAT Genius uses for Reading Comprehension (as described on our website). We break down the 261 Reading Comprehension questions as follows:

Integrated Reasoning

The main Official Guide (part of this bundle) includes online access to 58 Integrated Reasoning practice questions. The IR set includes 8 new questions that we have not seen before, plus all 50 questions from the prior 2017 edition. The 58 questions consist of the following four types:
Multi-Source Reasoning – 21 (3 new)
Table Analysis – 7 (1 new)
Graphics Interpretation – 12 (2 new)
Two-Part Analysis – 18 (2 new)

The GMAC classifies question difficulty into three categories of Easy / Medium / Hard as follows:
Multi-Source Reasoning – 6 / 7 / 8
Table Analysis – 3 / 1 / 3
Graphics Interpretation – 4 / 3 / 5
Two-Part Analysis – 5 / 7 / 6
Total – 18 / 18 / 22

Out of the 50 questions that carry over from the 2017 edition, the GMAC has reclassified the difficulty of 33 questions. For IR, GMAT Genius classifies question difficulty into the same three categories. Except for Two-Part Analysis, our assessment skews significantly easier, and contains notable differences from the GMAC. Our difficulty assessment is only 8.1% correlated with the GMAC’s assessment, clearly showing that there is tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown of Easy / Medium / Hard:
Multi-Source Reasoning – 9 / 11 / 1
Table Analysis – 3 / 4 / 0
Graphics Interpretation – 3 / 7 / 2
Two-Part Analysis – 2 / 10 / 6
Total – 17 / 32 / 9

Online Interface

Each Official Guide book includes an access code (see inside front covers) that provides 12-month usage of an online version of the book. 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 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 40-page Math Review section 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. Similarly, the brief introductions to the concepts tested on the verbal section are highly inadequate. We recommend that you use additional study materials to learn the math and verbal concepts.

Although all questions include answer explanations, many GMAT test takers are far from satisfied with these explanations. Math explanations can be brief and hard-to-understand for non-advanced students, and are sometimes convoluted or inefficient. Most GMAT test takers consider the Sentence Correction explanations quite cryptic. The Critical Reasoning and Reading Comprehension explanations, however, are reasonably good overall.

CONCLUSIONS

The Official Guide Bundle has three primary weaknesses, in our opinion:

1. An insufficient amount of difficult practice questions, particularly based on GMAT Genius’ assessment of difficulty. We are especially dismayed to see the net loss of 30 Hard-difficulty Quant questions (13 Problem Solving and 17 Data Sufficiency) based on GMAC’s difficulty assessment compared to the 2017 edition.
2. Math answer explanations that are too often either brief or convoluted and Sentence Correction explanations that are too cryptic.
3. Contrary to what the back covers of the books claim, questions are not fully presented in order of progressive difficulty for Reading Comprehension in the main OG, for Data Sufficiency in the Quant OG, and for Critical Reasoning and Sentence Correction in the Verbal OG.

Despite these flaws, the 2018 GMAT Official Guide Bundle is an essential source of GMAT practice. We believe that every GMAT aspirant must use all three Official Guide books (this or the prior edition). If you already have the 2017 editions of the Official Guides, however, the replacement of 106 math questions and 106 verbal questions is not sufficient to make this edition worth purchasing.

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

Overview of 2018 GMAT 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. This book has no overlap in practice questions with the Quant and Verbal Official Guides.

The 2018 GMAT Official Guide contains 130 new questions out of the 957 total questions (including Integrated Reasoning). Excluding the 100 questions in the Diagnostic Exam section of the book, the new questions represent just over 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 Official Guide contains 254 Problem Solving questions, including the 24 Problem Solving questions in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

The Problem Solving section contains 35 new questions, with difficulty of Easy / Medium / Hard as follows: 22 / 7 / 6. This is in lieu of 35 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 8 / 3 / 24. Unlike in prior years, the GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment of this section skews significantly easier, and contains notable differences from the GMAC’s assessment. Our difficulty assessment is only 69.9% correlated with the GMAC’s assessment, demonstrating tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown:

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 254 Problem Solving questions as follows:

Here’s a list of the 35 new Problem Solving questions:
3, 5, 6, 16, 22, 23, 24, 26, 33, 34, 40, 42, 50, 53, 55, 60, 68, 69, 72, 79, 81, 85, 90, 96, 98, 104, 122, 125, 139, 140, 151, 173, 201, 224, 229

Here’s a list of the 230 Problem Solving questions, excluding those in the Diagnostic Exam, categorized by primary math concept:

Data Sufficiency

The 2018 GMAT Official Guide contains 198 Data Sufficiency questions, including the 24 Data Sufficiency questions in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

The Data Sufficiency section contains 26 new questions, with difficulty of Easy / Medium / Hard as follows: 11 / 10 / 5. This is in lieu of 26 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 3 / 4 / 19. 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 56.0% correlated with the GMAC’s assessment, demonstrating tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown:

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 198 Data Sufficiency questions as follows:

Here’s a list of the 26 new Data Sufficiency questions:
233, 258, 260, 262, 266, 267, 273, 274, 276, 277, 278, 282, 284, 287, 288, 292, 293, 300, 306, 313, 326, 334, 339, 376, 382, 391

Here’s a list of the 174 Data Sufficiency questions, excluding those in the Diagnostic Exam, categorized by primary math concept:

Sentence Correction

The 2018 GMAT Official Guide contains 158 Sentence Correction questions, including the 18 Sentence Correction questions in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

The Sentence Correction section contains 21 new questions, with difficulty of Easy / Medium / Hard as follows: 4 / 4 / 13. This is in lieu of 21 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 3 / 5 / 13. The GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment skews noticeably easier, and contains notable differences from the GMAC. Our difficulty assessment is only 56.8% correlated with the GMAC’s assessment, clearly showing that there is subjectivity involved in assessing question difficulty. Here’s our breakdown:

Although Sentence Correction questions typically entail multiple grammar concepts (as described on our website), GMAT Genius classifies questions based on our assessment of the primary tested concept. We classify the 158 Sentence Correction questions as follows:

Here’s a list of the 21 new Sentence Correction questions:
674, 680, 684, 685, 699, 702, 717, 735, 743, 745, 750, 751, 763, 770, 777, 780, 781, 782, 784, 796, 799

Here’s a list of the 140 Sentence Correction questions, excluding those in the Diagnostic Exam, categorized by primary grammar concept:

Critical Reasoning

The 2018 GMAT Official Guide contains 141 Critical Reasoning questions, including the 17 Critical Reasoning questions in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

The Critical Reasoning section contains 19 new questions, with difficulty of Easy / Medium / Hard as follows: 6 / 2 / 11. This is in lieu of 19 questions from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 6 / 3 / 10. The GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Our assessment skews slightly easier, but contains notable differences from the GMAC. Our difficulty assessment is 74.1% correlated with the GMAC’s assessment, clearly indicating subjectivity involved in assessing question difficulty. Here’s our breakdown:

We have grouped the questions based on the question type categorization that GMAT Genius uses for Critical Reasoning (as described on our website). We break down the 141 Critical Reasoning questions as follows:

Here’s a list of the 19 new Critical Reasoning questions:
546, 550, 554, 556, 561, 575, 589, 599, 626, 627, 631, 634, 635, 640, 643, 651, 656, 660, 661

Here’s a list of the 124 Critical Reasoning questions, excluding those in the Diagnostic Exam, categorized by CR question type:

Reading Comprehension

The 2018 GMAT Official Guide contains 156 Reading Comprehension questions across 33 passages, including the 17 Reading Comprehension questions in 3 passages in the Diagnostic Exam portion of the book. The GMAC classifies question difficulty into three categories as follows:

In the Reading Comprehension 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, Easy, Medium, and Hard difficulty questions are interspersed. The following table shows the question numbers for each difficulty level:

The Reading Comprehension section contains 21 new questions in 6 passages, with difficulty of Easy / Medium / Hard as follows: 7 / 14 / 0. This is in lieu of 21 questions in 4 passages from the 2017 edition that have been removed, with difficulty of Easy / Medium / Hard as follows: 3 / 13 / 5. The GMAC has not reclassified the difficulty of any question.

GMAT Genius classifies question difficulty into five categories. Whereas the GMAC assigns the same difficulty to all questions for a given passage (except in the Diagnostic Exam section), GMAT Genius assesses the difficulty of each question individually. Our assessment skews slightly harder, but contains notable differences from the GMAC. Our difficulty assessment is only 57.6% correlated with the GMAC’s assessment, in large part due to different difficulty assessment methodologies. Here’s our breakdown:

We have grouped the questions based on the question type categorization that GMAT Genius uses for Reading Comprehension (as described on our website). We break down the 156 Reading Comprehension questions as follows:

Here’s a list of the 21 new Reading Comprehension questions: 412 to 418, 439 to 441, 467 to 470, 514 to 516, 537 to 540

We have not provided a list of Reading Comprehension questions by category because it makes sense to practice on one passage at a time, rather than attempting all the Primary Purpose questions (for example) at one go.

Integrated Reasoning

The 2018 GMAT Official Guide includes online access to 58 Integrated Reasoning practice questions. The IR set includes 8 new questions that we have not seen before, plus all 50 questions from the prior 2017 edition. The 58 questions consist of the following four types:
Multi-Source Reasoning – 21 (3 new)
Table Analysis – 7 (1 new)
Graphics Interpretation – 12 (2 new)
Two-Part Analysis – 18 (2 new)

The GMAC classifies question difficulty into three categories of Easy / Medium / Hard as follows:
Multi-Source Reasoning – 6 / 7 / 8
Table Analysis – 3 / 1 / 3
Graphics Interpretation – 4 / 3 / 5
Two-Part Analysis – 5 / 7 / 6
Total – 18 / 18 / 22

Out of the 50 questions that carry over from the 2017 edition, the GMAC has reclassified the difficulty of 33 questions. For IR, GMAT Genius classifies question difficulty into the same three categories. Except for Two-Part Analysis, our assessment skews significantly easier, and contains notable differences from the GMAC. Our difficulty assessment is only 8.1% correlated with the GMAC’s assessment, clearly showing that there is tremendous subjectivity involved in assessing question difficulty. Here’s our breakdown of Easy / Medium / Hard:
Multi-Source Reasoning – 9 / 11 / 1
Table Analysis – 3 / 4 / 0
Graphics Interpretation – 3 / 7 / 2
Two-Part Analysis – 2 / 10 / 6
Total – 17 / 32 / 9

Online Interface

The 2018 GMAT 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 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. Similarly, the brief introductions to the concepts tested on the verbal section are highly inadequate. We recommend that you use additional study materials to learn the math and verbal concepts.

Although all questions include answer explanations, many GMAT test takers are far from satisfied with these explanations. Math explanations can be brief and hard-to-understand for non-advanced students, and are sometimes convoluted or inefficient. Most GMAT test takers consider the Sentence Correction explanations quite cryptic. The Critical Reasoning and Reading Comprehension explanations, however, are reasonably good overall.

Conclusions

The 2018 GMAT 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. We are especially dismayed to see the net loss of 32 Hard-difficulty Quant questions (18 Problem Solving and 14 Data Sufficiency) based on GMAC’s difficulty assessment compared to the 2017 edition.
2. Math answer explanations that are too often either brief or convoluted and Sentence Correction explanations that are too cryptic.
3. In the Reading Comprehension 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 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 2018 GMAT Official Guide Bundle. If you already have the 2017 edition of this book, however, the replacement of 61 math questions and 61 verbal questions is not sufficient to make this edition worth purchasing.