Everything You Need to Know About the New Official Guides - Part 1
The new Official Guide books are here! Arent you excited?!?
Okay, I realize that most people probably arent as excited as I am. But there are still some interesting and useful things to know about these new books as you get ready to take the GMAT. So lets talk about it!
In this installment, Ill discuss additions and changes to quant sections for The Official Guide for GMAT Review 2016, aka the OG or the big book. Keep an eye out for later installments, in which Ill discuss the Verbal section of the big book, as well as the Quantitative Review and Verbal Review books. Ill also be providing you with a list of the new questions, in case you decide to study from both the 2015 and 2016 editions.
If you havent already bought your official guide books, then do buy these latest editionssure you might be able to get a discount on the 2015 editions, but since you have to spend money anyway, you might as well work from the latest and greatest.
If you have already bought the older editions and are debating whether to buy the new ones, too, then youve got a decision to make. On the one hand, there are a lot of great new questions in the 2016 editions. On the other, the 2015 edition already has a ton of problems; you may not need even more. If it were me, Id wait until Id used up the ones in the materials I already have. If I still felt that I needed more beyond that, then Id consider getting one or more of the new books.
Whats new in OG 2016?
Approximately 25% of the questions are brand new, and there are some beauties in the mix. As I worked through the problems, I marveled anew at the skill with which the test writers can produce what I call elegant problems. On the quant side, I saw example after example in which the problem can be solved with little to no computation as long as you can decode and understand the fundamental concept underlying the problemthats the real test-taking skill!
Rich DAmato, spokesperson for GMAT, confirmed that a decent number of the new questions were produced relatively recently; that is, youll be seeing questions that were on the real exam not too long ago. (The older questions are still great study questions, too; the GMAT is a standardized test so, by definition, the test makers cant change things too drastically or rapidly. There can be some mild trends over time, though. For example, the test makers may decide that certain idioms should be retired from or introduced for Sentence Correction problems.)
The opening chapters of the book describe how the GMAT works and how to study for the test; these sections have not changed. Nor has the Math Review (chapter 4). This is no surpriseagain, the GMAT is a standardized test and, as such, it remains very consistent over time. The Diagnostic test in chapter 3 also has not changed.
Whats new in Quant?
Overall, I noticed multiple new problems that crossed two or (occasionally) even three content areas. For instance, #18 is a geometry question that also crosses into percents, as does overlapping sets Problem #91. I chose those two examples on purpose so that I could also point this out: fractions and percents, in particular, are really good concepts to cross over into any other content area, so make sure you have a very solid foundation in both fractions and percents.
I also noticed a few visual questionsa couple of 3-D geometry and some coordinate plane problems that were made much harder by my general tendency to struggle with this kind of visual stuff. If youre like me, beware; you may decide ahead of time that you want to bail immediately on 3-D or other problems that have a heavy visual component.
Problem Solving
Of the 230 questions in the Problem Solving (PS) section, 58 are new. (Disclaimer: I hope I counted correctly for all of these sections, but Ive been going through about 1,500 questions and hundreds of pages quickly in order to get this review out to you right away. So please forgive me if I miscounted anything! Ill correct any errors as soon as I find out about them.)
I noticed a number of what Ill call practical questions: the question, usually a story problem, reads like something you might be asked to figure out in the real world. Problem #11, for example, asks you to figure out the minimum number of questionnaires youd need to mail in order to achieve a certain desired number of responses. (The problem includes an assumed response rate.)
Note: I cant actually reproduce the text of the question for copyright reasons, but Im citing the problem number so that you can look it up if you do decide to buy the book.
Problem #39 can literally be counted out on your fingersas long as you understand what youre being asked to do. Be careful with definitions!
I also saw several problems that seriously disguised what the question was getting at. I dont want to spoil you for the questionsbetter if you can figure it out for yourself!but take a close look at #68 and #83. On the surface, these would be classified as algebra. But at least one can be done more easily using a different set of concepts. (Ill tell you at the end of this article. But dont look until youve tried to figure it out yourself!)
I used smart numbers to solve a number of the problems and I also worked backwards multiple times. In other words, these strategies are just as important as they always were. I did notice one question (#99) on which we could use smart numbers but the form of the answers indicated that itd almost certainly be easier to do algebra. Look at the problem; youll see what I mean!
Finally, lets talk about those elegant questions. If you can understand the concepts underlying #97, then you barely need to calculate anything at alleven though it looks as though youre going to need to do some annoying algebra to answer the problem. Likewise, #107 has a huge disguise that, once uncovered, allows you to answer in two seconds without calculating anything at all. (Again, Ill tell you what this is at the end of this article.)
Data Sufficiency
Of the 174 Data Sufficiency (DS) problems, 45 are new to this edition of the OG.
Continuing on the theme from PS, I was really struck by the number of new story problems for which translation is the whole key. If you translate carefully and accurately, then you dont need to do anything more to solve. For example, #38 looks particularly nasty. Translate that thing very carefully, though, and you wont have to do any messy calculations to answer. Problem #83 is another example; the story is pretty confusing, but if you can lay out the parts carefully and clearly, then the rest of the problem is more about logic than math.
Next, I used testing cases numerous times; as with PS, the standard test-taking strategies are still in full evidence on DS. I also noticed that, as before, its crucial to make sure you know what you were asked to find. This is true on PS too, of course, but DS tends to set more traps around solving for the wrong thing. Check out #39. You cant find t by itself, but you can find [pmath]t^2[/pmath], and thats good enough to solve.
So what were all those cool disguises and tricks you mentioned?
Here you go. Again, do not read this until you have worked on these problems yourself! If you can figure out whats going on yourself, the lesson will stick much better in the end. :)
PS #68 and #83. These two problems share a consecutive integer disguise. The givens can be read to mean consecutive integers (the second one has to be rearranged to do so) and, since in each case the two terms multiply to an integer, that tells you that youre dealing with the factors of that integer. For instance, in #68, the factors of 24 are (1, 24), (2, 12), (3, 8), and (4, 6). BUT note that the problem does not actually mention factors or specify positive numbers, so you also have to take into account that the pairs could be negative.
Next, you know that they have to be consecutive odds or consecutive evens, so the only two pairs that work are (4, 6) and (-4, -6). From there, you can figure out the answer. Problem #83 has a similar disguise, although it can also be solved via quadratic equations.
PS #97. The question asks you to maximize the depth, [pmath]N(t)[/pmath]. The [pmath]-20(t-5)^2[/pmath] term has that negative sign out front, so it could reduce the depth, so you need to minimize the negative value. How? Make the [pmath](t-5)[/pmath] term equal to zero!
PS #107. I love this one. Its a weighted average question in disguise. The formula [pmath]x + y = 1[/pmath] signifies that the two weightings add up to 100%: [pmath]x + y = [/pmath]100%, where[pmath]x[/pmath]and [pmath]y[/pmath]are the two weightings. The formula [pmath]100x + 200y[/pmath] signifies the weightings that youre applying to each of the two endpoints, 100 and 200. The weighted average must be somewhere between the two starting numbers / endpoints, so only two of the roman numerals can work.
DS #38. The question tells you to set [pmath](1/12 + kv^2)[/pmath] equal to [pmath]5/12[/pmath]. Then it asks you for v. If you know k, then you can find v. So the real question is whether the statement allows you to find k. Statement (1) obviously does, and statement (2) also does, because it gives you another equation: [pmath](1/12) + k(30)^2= 1/6[/pmath].
DS #83. There are [pmath]x[/pmath]processors. Each processor can process up to [pmath]y[/pmath] calls. Think about what this meansmaybe even draw a picture. Note that [pmath]x[/pmath] has to be at least 1 and [pmath]y[/pmath] has to be at least 1. If you have [pmath]x = 1[/pmath] processor that can process [pmath]y = 500[/pmath] calls, then sure, you can process 500 calls at once. If you have [pmath]x = 10[/pmath] processors that can process [pmath]y = 10[/pmath] calls each, then nope, you cant process 500 calls at once.
So you need to know something about [pmath]x[/pmath]and [pmath]y[/pmath]in order to answer. It looks, then, like statements (1) and (2) cant work alone, since each talks about only one variable. But dont forget the constraint that each has to be at least 1!! If you have [pmath]x = 600[/pmath] processors, then you can definitely process 500 calls, since each processor has to be able to process at least one call.
What about Verbal? And the other books?
Next time, well dive into the verbal sections of the Big OG. Then, well discuss the quant and verbal supplements, and finally, Ill provide you with lists of the new questions in each book and also the new question numbers for the old questions that remain in the book from the last edition.
Happy studying!