Have you ever gotten a GMAT question wrong because you thought you were supposed to take a square root and get two different numbers but the answer key said only the positive root counted? Alternatively, have you ever gotten one wrong because you took the square root and wrote down just the positive root but the answer key said that, this time, both the positive and the negative root counted? What’s going on here?

There are a couple of rules we need to keep straight in terms of how standardized tests (including the GMAT) deal with square roots. The Official Guide does detail these rules, but enough students have questioned us about the OG explanation that we decided to write an article in hopes of clearing everything up. : )

I want to mention one thing before we dive in: the vast majority of the time, both roots do count, and it’s rare to miss an official question as long as you do take both roots. You could just decide that you’re not going to worry about it and you’re going to solve normally (always taking both square roots). Many students do still stress about this topic, though, so if you’re in that group, read on!

Doesn’t the OG say that we’re only supposed to take the positive root?

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In an earlier post, we tackled a medium-level GMATPrep weighted average question; click here to read that article before reading this one. This week, we’re trying a harder GMATPrep  weighted average question in order to test whether you learned the concept as well as you thought you did. : )

As we discussed earlier, every weighted average problem I’ve seen (so far!) on GMATPrep is a Data Sufficiency question. This doesn’t mean that they’ll never give us a Problem Solving weighted average problem, but it does seem to be the case that the test-writers are more concerned with whether we understand how weighted averages work than with whether we can actually do the calculations. Last week, we focused on understanding how weighted averages work via writing some equations. We’ll try to apply that understanding to our harder problem this week, along with a more efficient solution method.

Let’s start with a sample problem. Set your timer for 2 minutes. and GO!

* A contractor combined x tons of gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x?

(1) y = 10

(2) z = 16

There are two kinds of gravel: 10% gravel and 2% gravel. These are our two sub-groups. When the two are combined (in some unknown “ for now! “ amounts), we get a 3^rd kind:5% gravel. The number of tons of 10% gravel (x) and the number of tons of 2% gravel (y) will add up to the number of tons of 5% gravel (z), or x + y = z. We need to find the number of tons of 10% gravel used in the mixture.

The problem this week throws in a new wrinkle: we’re not just trying to calculate a ratio this time. We have to have enough info to calculate the actual amount of 10% gravel used. Last week, we never had to worry about the actual number of employees. We’ll have to keep that in mind to see how things might change.

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This week, we’re going to tackle a GMATPrep question from the quant side of things. We’ll tackle a medium-level question this week in order to learn how to master weighted average questions in general, and in the next article, we’ll try a very hard one “ just to see whether you learned the concept as well as you thought you did. : )

Before we begin, I want to mention that every weighted average problem I’ve seen on GMATPrep is a Data Sufficiency question. This doesn’t mean that they’ll never give us a Problem Solving weighted average problem, but it does seem to be the case that the test-writers are more concerned with whether we understand how weighted averages work than with whether we can actually do the calculations. So we’re going to work on that conceptual understanding today and then we’ll discuss a neat calculation shortcut next week (built on the same principles!), just in case we do need to solve.

Let’s start with a sample problem. Set your timer for 2 minutes. and GO!
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I’ve been speaking with a lot of students recently who are really struggling with translation problems “ even when they can figure out how to translate, they end up taking way too much time on the problem.

So let’s try this GMATPrep problem; set your timer for 2 minutes and GO!

If Bob produces 36 or fewer items in a week, he is paid x dollars per item. If Bob produces more than 36 items in a week, he is paid x dollars per item for the first 36 items and [latex]1frac{1}{2}[/latex] times that amount for each additional item. How many items did Bob produce last week?

(1) Last week Bob was paid a total of $480 for the items that he produced that week.

(2) This week Bob produced 2 more items than last week and was paid a total of $510 for the items that he produced this week.

Ugh. Okay, obviously we’re going to have to translate, because we’ve got a story going on here. It also looks like there’s going to be some algebra involved. Let’s dig in.

I’m now Bob. (Put yourself in the story; that’ll make things a little bit easier.) I can make either 36 or fewer items in one week or more than 36 items. How am I going to get paid? For the first scenario, I can figure out my pay by multiplying the number of items by x. If I make exactly 36 items, I’ll get paid 36x. If I make 33 items, I’ll get paid 33x. Hmm. I guess I should assign a variable for the number of items I make; let’s call that N.

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As we discussed in the first half of this series, Building Your Game Plan, during the last 7 to 14 days before you take the real test, your entire study focus changes. In this article, we’re going to discuss the second half of this process: how to review. (If you haven’t already read the first half, do so; then come back here and continue with the second part.)

What is a Game Plan?

The first half of the article, found at the link above, discusses how to build and implement your Game Plan. At the same time, you’re also going to be reviewing, so let’s talk about that!

What to Review

Part of the game planning process is determining your strengths and weaknesses (which is why I recommended that you read the Building Your Game Plan article first). You’ll then need to consider your list of strengths and weaknesses from the point of view of how frequently those topics or question types tend to be found on the real exam. Struggling with probabilities or evaluate the conclusion Critical Reasoning questions? Neither type is that common and you have just two weeks left; drop them from your list. Struggling with exponential or quadratic equations or inference Reading Comprehension questions? Those are much more common, so they need to be on the review list.

If you’re not sure how frequently a particular type of content or question appears on the exam, look on the forums. (I’m not providing a list in this article because these frequencies can change over time; I don’t want people reading this in future to be misled when things do change.)

How to Review

How you review is going to vary somewhat depending upon whether you’re reviewing a strength or a weakness. You do NOT want to do the same kind of review for everything, but you DO want to review both strengths and weaknesses. Below, I will discuss easier-for-you and harder-for-you questions, since we don’t actually know any difficulty levels when taking the test. Easier-for-you means that you find the question fairly straightforward and you expect to answer it correctly without needing extra time, though you may sometimes make a careless mistake. Harder-for-you means that this question is more of a struggle, though you still will answer some of these correctly.

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Are you aware that, during the last 7 to 14 days before you take the real test, your entire study focus changes? This is crucially important “ I cannot count the number of people who don’t realize what they need to do leading up to Real Test Day and so miss the chance to maximize their scores.

There are two levels to this discussion: (1) building a game plan and (2) reviewing. This post will cover the first topic and my next post will cover the second one.

Throughout both articles, I’m going to discuss the ideal scenario: the one in which you have a full 2 weeks to conduct your review. This review can be compressed into a 7 to 10 day period, if needed “ if so, just note that you are going to take only one practice test, not two, and you of course won’t be able to do as much review because you won’t have as much time.

Warning: please do not literally compress everything discussed into 7 days instead of 14. It’s a terrible idea to take the last week off of work and try to study for 6 to 8 hours a day. You’ll just burn yourself out.

Focus Shift

In the last two weeks before your test, you’re going to make a major focus shift. You’re going to stop trying to learn a bunch of new things in order to improve your score and instead acknowledge that your skills are what they are. They’re not going to change an enormous amount in the last two weeks; you can tweak some things, but now is not the time to change major strategies across an entire question type. Further, it would be a mistake to spend your last two weeks entirely focused on your weaknesses; if you do that, then you won’t be prepared to excel on your strengths.

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This is the latest in a series of How To Analyze articles that began with the general How To Analyze A Practice Problem article (click on the link to read the original article). This week, we’re going to analyze a specific IR question from the Graph prompt category.

Let’s try out the question: here it is. Just in case that link changes, you can also click on this link to go to the mba.com website, and then, about halfway down the page, click on the Graphics Interpretation link. We’re going to try the 2nd of the 4 questions. If you’re going for an average IR score, give yourself 2.5 minutes; if you’re going for a really good score, give yourself between 1.5 and 2 minutes.

Note: when you are done, do NOT click the next button. Just leave it up on the screen and come back here.

First, read the complete solution to the problem. In that article, I discussed how I was able to answer one of the questions correctly even though I wasn’t 100% confident that I understood part of the description of the graph. I also talked about an important lesson I learned regarding how to read the questions.

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Did you know that you can attend the first session of any of our online or in-person GMAT courses absolutely free? We’re not kidding! Check out our upcoming courses here.

How do you study? More importantly, how do you know that the way in which you’re studying is effective—that is, that you’re learning what you need to learn to improve your GMAT score? Read on!

In the first part of this series, we discussed how to get started with your GMAT study plan: setting up your timeframe, picking out your materials, and so on. (If you haven’t read it yet, please do so before you continue here!) In today’s installment, we’ll talk about how to study and make progress over the actual length of your study timeframe. Read more

Did you know that you can attend the first session of any of our online or in-person GMAT courses absolutely free? We’re not kidding! Check out our upcoming courses here.

Just starting out? Or maybe you’ve been studying for weeks already? Perhaps you’ve already taken the official test once but want another crack at it? Whatever stage you’re at, you need a GMAT study plan, so that’s what we’re going to talk about this week: how to develop your own personalized GMAT study plan. (Note: this is an update from the original article about 2.5 years ago. If you run across the older version, ignore it; use this newer one instead!) Read more

This is the latest in a series of How To Analyze articles that began with the general How To Analyze A Practice Problem article (click on the link to read the original article). This week, we’re going to analyze a specific IR question from the Multi-Source Reasoning prompt category.

These prompts typically come with multiple questions (similar to a Reading Comp passage). First, give yourself about 2 to 2.5 minutes to read the prompt and take short notes. Then take up to about 2 minutes to answer the question.

Click on this link for the prompt and question. In case that link changes or gets broken, I’ve also included the text below “ but it’s best to use the link if it works because then you’ll be doing the problem in its official format. When you’re done, leave that page open (don’t click next) and come back here to discuss the solution.

Multi-Source Reasoning prompts consist of 2 or 3 tabs of information. Here is the prompt:

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