The Official Guide 2021 Review and Highlights

GMAC published the 2021 edition of its Official Guide series in late June and we’ve got all of the highlights for the main guide.

Is it worth buying?

Definitely. I wouldn’t study for the GMAT without using at least the main official guide (OG) book. There are four books in all:

  1. The GMAT Official Guide (aka, the main OG): Contains more than 1,000 problems across all three multiple-choice sections of the exam (Quant, Verbal, and Integrated Reasoning) as well as dozens of sample essay prompts.
  2. The GMAT Official Guide Quantitative Review: Contains more than 350 Quant problems that do not appear in the main OG.
  3. The GMAT Official Guide Verbal Review: Contains more than 350 Verbal problems that do not appear in the main OG.
  4. GMAT Official Advanced Questions: Contains 300 hard Quant and Verbal problems that do not appear in any of the other OGs.

The main OG contains so many problems that I find most students don’t need the Quant and Verbal-only books, but they’re available if you want more. If you’re going for a 700+ kind of score, then you may also want the Advanced OG (but start with the main OG unless your score is already in the upper 600s).

How is it different from the prior edition (Official Guide 2020)?

There are 92 new problems:

  • 32 Problem Solving
  • 10 Data Sufficiency
  • 19 Critical Reasoning
  • 31 Sentence Correction

There are no new Reading Comprehension passages or problems. In addition, one Critical Reasoning question was removed from the book, so the total number of CR problems increased by 18, not 19. No other problems were removed from the book.

GMAC did remove the Diagnostic Test chapter, which contained 100 problems, but you still have access to all of these problems at their Efficient Learning online platform (you get access to this platform for 1 year with your purchase of the book). You’ll find the 100 Diagnostic problems in the “Online Exclusive” problem bank, and you’ll have access to a number of Integrated Reasoning practice problems that are also available only online. And, as a bonus, the online platform contains all of the problems that are printed in the book; you can create problem sets (more on this below), practice time management, and track certain performance metrics.

There’s one interesting new feature this year: digital flash cards to help you study. I haven’t tried them yet so can’t tell you whether they’re good, but I’m a big fan of flash cards in general. They’re great for anything you need to memorize—facts, formulas, and what I call Know the Code takeaways. These takeaways come in the form “When I see _____” (on the front side of the flash card) and “I’ll think / do ______” (on the back side of the flash card). For example: When I see a comma which vs. comma –ing difference in the answers on an SC problem, I’ll think “modifiers” and figure out what the modifier is referring to.

If you’re debating between buying OG2020 and OG2021, I’d go for 2021. You’ll have all of the same problems that are in OG2020, plus 92 additional, brand-new problems as well as access to the new flash cards.

How should I use the OG in my studies?

If you’re using our study materials, we’ve classified all of the OG problems by problem type and by chapter / content area from our books. Anyone can access these classification lists by creating a free Atlas GMAT Starter Kit account on our website. You’ll find the OG problem lists under Official Guide Resources on the left-hand menu bar. (The Starter Kit has a bunch of other free resources as well, FYI.)

I would also take a look at this blog series on creating your own problem sets. You’ll use the problems in different ways during different stages of your studies and that series explains what to do when.

Are there any trends in the new problems?

There are a lot of really interesting new problems! I can’t, unfortunately, show any of them to you (copyright law…), but I’ll tell you what I think about some of them and you can look them up yourself in your own copy of the book. 


Overall, I noticed a ton of stories and a lot of opportunities to logic something out or to estimate. There are also some pure math problems, but there is a definite trend around the ability to think logically about math. (And I love that because it makes the test a lot easier to take—once you train yourself to think logically about math. Bonus: That ability will help you in b-school and at work.)

There were also some beautiful traps—the test writers really are masters at figuring out how to tempt us to go down the wrong path. (Seriously, I consider them artists in this way!)

Here are a few of my favorite Problem Solving and Data Sufficiency problems that are new to OG 2021. When you have your copy, try the problems first and then read what I thought.

PS #94

    • Summary: Gives us kilometers per hour and asks for the answer in miles per hour (along with another calculation).
    • Why I like it: The middle answer is the answer if you don’t convert to miles (ie, it’s a trap!). From there, you can eyeball to tell whether the answer should be greater or less than that trap value, so that gets you down to two answers. And you can use common Fraction Decimal Percent (FDP) conversions (0.625 = 5/8) and estimation to get down to the single correct answer without too much trouble.

PS #117

    • Summary: What I call a Wall of Text (WoT) problem. Complicated story with data for each month of an entire year—and you do actually need to calculate profit for the whole 12 months.
    • Why I like it: You can balance groups of months and just find the aggregate difference. For example, for 3 months, you lose $32K per month and for 3 months you gain $36K per month. For each pair of win-loss months, then, you gain $4K, so total you gain $12K, which represents your profit for 6 months of the year. Keep going from there to get your answer.

PS #259

    • Summary: This is the hardest of the new-to-2021 PS problems. It’s a parallelogram, part of which is split into a triangle and they want to know what fraction the triangle represents of the rest of the parallelogram (not the whole thing).
    • Why I like it: The diagram is drawn to scale, so you know immediately that (A) can’t be correct (too big) and (E) is almost certainly too small. Down to three answers in like 5 seconds. Next, eyeball the triangle as a fraction of the whole parallelogram. That’s about 1/4…but that’s not what they asked. And, hey, that value is in the answers, so cross it off. There are only two answers left, one greater than 1/4 and one less than 1/4. Logic it out: If the triangle as a fraction of the whole parallelogram is 1/4, then the triangle has to be a greater fraction of just part of the parallelogram, since part of the parallelogram is smaller than the whole parallelogram. Done.

DS #488: This is my favorite one of them all! This looks like an easier problem but it’s one of the highest-numbered in the chapter…and for good reason.

    • Summary: Another WoT (wall of text) problem but the question seems really easy: What’s the discounted price of the second shirt?
    • Why I like it: Take your time on understanding the story. If you spot what this thing is really asking, the solution is straightforward. If you don’t, you’ll almost certainly fall into a trap. The discounted price of the second shirt is the same as the cost to manufacture the shirt. The story literally describes selling the shirt at cost! One of the two statements gives you the manufacturing cost outright and the other statement is useless by itself—once you know that you’re looking for the manufacturing cost.


In the Critical Reasoning chapter, 11 of the 19 new problems were Strengthen or Weaken. These two types are quite frequent on the real test. My favorite of the new problems is a Weaken (details below).

Each Sentence Correction problem tests multiple grammar rules, as always. I noticed a lot of sentence structure issues, parallelism and comparisons, and some really interesting issues around meaning.

Here are a few of my favorite new problems. When you have your copy, try the problems first and then read what I thought.

CR #707

    • Summary: Some people want to limit the amount of homework assigned to kids under the age of 12. But the average homework time for students of this age is only about 30 minutes per night, so the argument’s author disagrees and doesn’t think it’s necessary to limit homework. The question asks us to weaken the author’s conclusion.
    • Why I like it: The correct answer is so hard to spot! You actually have to bring in an understanding of statistics, so this is a great amalgamation of verbal and math skills. We accept as true the author’s statement that the average homework time for this group is ~30 minutes. But could it still be the case that some percentage of these students have hours of homework a night, even though the average for all students is only 30 minutes? Yes—if other students in this group have almost no homework at all, so that the average still comes out to ~30 minutes. And that’s what the correct answer establishes: that a lot of these students have very little homework (so a small subset of the total would have quite a bit of homework).

SC #854

    • Summary: The sentence structure of the original sentence is similar to this: “Although cats, sleeping all day in the heat of summer, by nighttime they begin to prowl around in the dark, hunting for prey.” The actual sentence is of course longer and more complicated, so it hides the fact that the opening Although clause has no verb.
    • Why I like it: This is a great introduction to overall sentence structure issues—all four wrong answers create “illegal” sentence structures and can be eliminated for that reason. It’s a great lesson in how to look at the overall sentence structure (vs. zeroing in on one specific / tiny / nitpicky grammar issue).

SC #867

    • Summary: The sentence structure of the original sentence is similar to this: “Although when a cat grooms itself, it can cough up a small hairball, it will not choke the cat, (ignoring the rest of the original sentence because it doesn’t matter for my example).” The first pronoun it refers to the cat but the second pronoun it refers to the hairball. Because you’re already primed to think that it = cat after the first instance, it’s confusing when you get to the second it. The cat will not choke the cat?
    • Why I like it: In the notes I took just after I tried this one for the first time, the first thing I wrote was “Clever.” I had to read the opening part of the sentence twice to understand what it was actually trying to say. What expands several hundred times? Presumably not the fish (imagine a trout expanding to the size of a whale…not going to happen!), so it must be the slime. (And the later, non-underlined portion of the sentence confirms this interpretation—but I hadn’t gotten there yet.) The fact that I couldn’t initially understand the meaning actually indicates the problem with this sentence: It’s ambiguous. The correct answer needs to be a lot more clear.

Anything else?

That’s it! But I will repeat what I said at the beginning. Don’t consider studying for the GMAT without getting yourself a copy of the OG. If you already have a copy of the 2020 edition, it’s not necessary to purchase the new edition. But if you don’t yet have a copy, I’d recommend getting OG 2021.

Good luck and happy studying! 

stacey-koprinceStacey Koprince is a Manhattan Prep instructor based in Montreal, Canada and Los Angeles, California. Stacey has been teaching the GMAT, GRE, and LSAT  for more than 15 years and is one of the most well-known instructors in the industry. Stacey loves to teach and is absolutely fascinated by standardized tests. Check out Stacey’s upcoming GMAT courses here.

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The Official Guide 2021 Review and Highlights