The other week, we discussed the overall process for Data Sufficiency. This week, we’re going to test out the process using a GMATPrep question “ and take a look at a couple of very common DS traps.

Set your timer for 2 minutes. and GO!

*  A bookstore that sells used books sells each of its paperback books for a certain price and each of its hardcover books for a certain price. If Joe, Maria, and Paul all bought books in this store, how much did Maria pay for 1 paperback book and 1 hardcover book?

(1) Joe bought 2 paperback books and 3 hardcover books for $12.50.

(2) Paul bought 4 paperback books and 6 hardcover books for $25.00.

Note that I haven’t listed the answer choices for you. Because DS answers are always the same, we should memorize them. If you don’t have them memorized yet, look back at the How DS Works article linked in the first paragraph.

All right, let’s tackle this problem.

Step 1: Read the Question Stem

The first sentence tells us that each paperback book sells for the same price and each hardcover book also sells for the same price (but possibly a different price than the paperback books).

The question asks how much Maria paid for 1 of each type of book. Is this a value or a yes/no question?

They’re asking for a specific amount; this is a value question. We’ve also got lots of words; we’re going to have to translate.

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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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In honor of Gabby Douglas’ gold medal win, as well as the U.S. women’s gymnastics team’s all-around gold medal win, here is an Olympics-inspired Data Sufficiency problem.

A particular gymnastics tournament awards a gold, a silver, and a bronze medal in each of four events: Floor, Beam, Bars, and Vault. A platinum Best All-Around medal is awarded to the competitor who gains the most points from winning the other medals: 3 points for gold, 2 points for silver, 1 point for bronze. If McKenzie won the Best All-Around medal, and no one can win more than one medal in any of the four events, did she win at least one gold medal?

1. All of the gold, silver, and bronze medals were won by fewer than six competitors, including McKenzie
2. Another competitor in the tournament has 8 points.

(A) Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

(B) Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

(C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

(D) EACH statement ALONE is sufficient.

(E) Statements (1) and (2) TOGETHER are NOT sufficient.

Choose your answer before proceeding!

First, you may ask, How could someone win the All-Around without winning a single gold medal?

Easy “ just imagine that McKenzie won ALL of the silver medals (8 points), and that no one else won more than one medal (the other medals are won by 8 separate people), so each person who has a gold has just 3 points, and each person who has a bronze has just 1 point.

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If the GMAT were a sport, it would definitely be baseball, and not just because it’s three and a half hours long. In baseball, you might dominate the minor league by hitting fastballs, but once you reach the show you’ll have to hit some change-ups and curveballs too. Not only is the GMAT going to throw you some hard problems, but once you start to do well, the GMAT will throw you something different. That’s why learning the types of trap answers can help you from falling for them. Here’s four types of curveballs that you want to be mindful of on test day.

If you test it, they will come.

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Today we’ve got an inequalities data sufficiency question on tap from GMATPrep. Set your timer for 2 minutes and go!

Is m + z > 0?

(1) m “ 3z > 0
(2) 4z “ m > 0

This is a yes/no data sufficiency question. I’m just going to remind myself of the rules: an always yes answer to a statement is sufficient, an always no answer is also sufficient, and a maybe or sometimes yes / sometimes no answer is not sufficient.
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Data sufficiency problems can be a lot of fun because we don’t actually have to solve all the way to the end of the problem. At the same time, data sufficiency problems can be maddening because of the way in which the information is worded. Often, especially on harder questions, the question stem or statements in a data sufficiency problem are worded in such a tricky way that we’re not sure of the significance of the information after we’ve read it.

This lesson is all about how to Rephrase the information in a more useful way. (For those who have taken or are planning to take our class, the Rephrasing lesson occurs during class 1, though I’ve changed the order in which the types are presented in this article.) Read more

The GMAT is a necessary hurdle on your way to business school, but sometimes it’s hard to see why. What do these multiple choice questions really have to do with a masters in business administration? If this question plagues you, take a look at this recent post from the GMAC. It explains exactly how two types of questions”data sufficiency and critical reasoning”measure abilities required by business schools.

Data Sufficiency. This question type, which requires you to determine what’s necessary to solve the problem, is ultimately a test of your ability to weed through minutiae for the important details. And sorting through information is an essential skill set, given the data-rich nature of the modern business environment, says Booth School of Business professor Pradeep Chintagunta. To successfully manage in this environment requires translating the data into usable information, he says, adding, The skills tested by the Data Sufficiency part of the test are consequently critical to managerial decision making.

Critical Reasoning. These questions probe your ability to evaluate the relative strengths of arguments. If you can handle a critical reasoning question, you’re prepared for collaborative b-school projects requiring you to judge others’ ideas. And those projects, in turn, are designed to get you ready for the real world. MBA programs can provide students with decision-making processes, says Valter Lazarri, MBA director of the SDA Bocconi School of Management, Milan, but they need a raw ability to connect facts, to detect patterns, to discriminate true causation from spurious correlations.

Of course, it is easier to sort through information when you understand its substance”hence our content-based curriculum.  And don’t fret if you’re struggling in these areas. With diligent practice, you can develop your natural abilities.

This week, we have a follow-on article from Chris Ryan, Manhattan GMAT’s Director of Instructor and Product Development. Chris introduced the concept of layering to us in this article on Sentence Correction. Layering is a technique used by a test writer to make a question more difficult. Today, Chris is going to show us how layering works in data sufficiency questions.

Note: I’ve repeated the introduction from the first article below, in case some of you haven’t read that one. If you did read the first one, the first few paragraphs will be review for you.

We all know that the GMAT is a computer adaptive test, and computer adaptive tests give us questions based on the difficulty level that we earn as we take the test. How do the test writers at ACT (the organization that writes the GMAT) determine which questions are harder than others?

First, ACT engages in a process called “normalization,” wherein all freshly written questions are tested by actual test takers to determine what percentage answer the questions correctly (we know these questions as experimental questions). If too many people answer correctly, the question may need to be toughened up. If too few people answer correctly, the question may need to be dumbed down. ACT is looking to assemble a pool of questions that covers a range of difficulty, from cakewalk to mind-bending, and the test takers help them do so.

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About 2 years ago, one of our L.A. Instructors, Mike Kim, suggested that we provide a math curriculum  for students who want a refresher on fundamental math topics (e.g.  fractions, algebra, etc.).  We thought it was a fantastic idea.  Being an extraordinarily productive guy, Mike went on to author the Foundations of GMAT Math Workshops I and II which take place online (it turns out there are too many fundamental math topics to teach in one sitting).

Now, the Foundations of Math Workshops will be available for free to any Manhattan GMAT course student.  If you are a course student, you can simply go to the website and add the Foundations workshops to your account.  You will immediately receive access to dozens of practice problems in your student center as well as class recordings, and you can attend the next scheduled Foundations workshops live.

For non-students, the Foundations of Math Workshops will each be available for only $95.  Additionally, if you end up signing up for a course after taking the Workshops, we’ll credit you whatever you spent on the workshops, so they’ll essentially wind up being free for you too.

Remember, these workshops review foundational math topics such as algebra, basic geometry, fractions, etc.  They’re very useful if you need a refresher because you haven’t seen the math in a long while, but if you’re comfortable with the math already you can feel free to go straight to the Official Guides, Strategy Guides, etc.

P.S.  The Foundations of GMAT Math Book is due out this Fall, as Mike’s original idea is taking multiple forms to reach as many people as possible.

Application season is starting to heat up again! For those of you just getting started, here’s an overview of “what’s what” with the GMAT.

What Is The GMAT?

The Graduate Management Admissions Test is a standardized test that many English-speaking business schools require applicants to take. The test is called a CAT, or Computer Adaptive Test, both because it is administered on a computer and because the test actually changes based upon how we answer the questions. The computer chooses what test questions to give us based upon our performance up until that point in the test. In a sense, we all take a different test, because the specific mix of questions any one person sees is based on that person’s performance during the test.

To register for the test or learn more information straight from the testwriters, go to www.mba.com.

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