If you’re going to do a great job on Data Sufficiency, then you’ve got to know how to Test Cases. This strategy will help you on countless DS problems.

Try this GMATPrep® problem from the free exams. Give yourself about 2 minutes. Go!

* “On the number line, if the number k is to the left of the number t, is the product kt to the right of t?

“(1) t < 0 “(2) k < 1” If visualizing things helps you wrap your brain around the math (it certainly helps me), sketch out a number line:

k is somewhere to the left of t, but the two actual values could be anything. Both could be positive or both negative, or k could be negative and t positive. One of the two could even be zero.

The question asks whether kt is to the right of t. That is, is the product kt greater than t by itself?

There are a million possibilities for the values of k and t, so this question is what we call a theory question: are there certain characteristics of various numbers that would produce a consistent answer? Common characteristics tested on theory problems include positive, negative, zero, simple fractions, odds, evens, primes—basically, number properties.

“(1) t < 0 This problem appears to be testing positive and negative, since the statement specifies that one of the values must be negative. Test some real numbers, always making sure that t is negative.

Case #1:

Testing Cases involves three consistent steps:

First, choose numbers to test in the problem

Second, make sure that you have selected a valid case. All of the givens must be true using your selected numbers.

Third, answer the question.

In this case, the answer is Yes. Now, your next strategy comes into play: try to prove the statement insufficient.

How? Ask yourself what numbers you could try that would give you the opposite answer. The first time, you got a Yes. Can you get a No?

Case #2:

Careful: this is where you might make a mistake. In trying to find the opposite case, you might try a mix of numbers that is invalid. Always make sure that you have a valid case before you actually try to answer the question. Discard case 2.

Case #3:

Hmm. We got another Yes answer. What does this mean? If you can’t come up with the opposite answer, see if you can understand why. According to this statement, t is always negative. Since k must be smaller than t, k will also always be negative.

The product kt, then, will be the product of two negative numbers, which is always positive. As a result, kt must always be larger than t, since kt is positive and t is negative.

Okay, statement (1) is sufficient. Cross off answers BCE and check out statement (2):

“(2) k < 1” You know the drill. Test cases again! Case #1:

You’ve got a No answer. Try to find a Yes.

Case #2:

Hmm. I got another No. What needs to happen to make kt > t? Remember what happened when you were testing statement (1): try making them both negative!

In fact, when you’re testing statement (2), see whether any of the cases you already tested for statement (1) are still valid for statement (2). If so, you can save yourself some work. Ideally, the below would be your path for statement (2), not what I first showed above:

“(2) k < 1” Case #1:

Now, try to find your opposite answer: can you get a No?All you have to do is make sure that the case is valid. If so, you’ve already done the math, so you know that the answer is the same (in this case, Yes).

Case #2: Try something I couldn’t try before. k could be positive or even 0…

A Yes and a No add up to an insufficient answer. Eliminate answer (D).

The correct answer is (A).

Guess what? The technique can also work on some Problem Solving problems. Try it out on the following GMATPrep problem, then join me next week to discuss the answer:

* “For which of the following functions f is f(x) = f(1 – x) for all x?

“(A) f(x) = 1 – x

“(B) f(x) = 1 – x²

“(C) f(x) = x² – (1 – x)²

“(D) f(x) = x²(1 – x)²

“(E) 

Key Takeaways: Test Cases on Data Sufficiency

(1) When DS asks you a “theory” question, test cases. Theory questions allow multiple possible scenarios, or cases. Your goal is to see whether the given information provides a consistent answer.

(2) Specifically, try to disprove the statement: if you can find one Yes and one No answer, then you’re done with that statement. You know it’s insufficient. If you keep trying different kinds of numbers but getting the same answer, see whether you can think through the theory to prove to yourself that the statement really does always work. (If you can’t, but the numbers you try keep giving you one consistent answer, just go ahead and assume that the statement is sufficient. If you’ve made a mistake, you can learn from it later.)

* GMATPrep® questions courtesy of the Graduate Management Admissions Council. Usage of this question does not imply endorsement by GMAC.

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The following excerpt comes from Top GMAT Prep Courses, a helpful resource for comparing your GMAT prep options, gathering  in-depth course reviews, and receiving exclusive discounts. Top GMAT Prep Courses had the chance to connect with Ron Purewal, one of Manhattan Prep’s veteran GMAT instructors, to ask questions about the GMAT that we hope all prospective MBA candidates will benefit from. Want more? Head on over to the full article!

What are the most common misconceptions of the GMAT that you notice on a regular basis?

“There are two BIG misconceptions in play here.

The first is “knowledge.” Too many people view this test as a monumental task of memorization. A test of knowing stuff. If you’re new to this exam, it’s understandable that you might think this way. After all, that’s how tests have always worked at school, right? Right. And that’s exactly why the GMAT doesn’t work that way. Think about it for a sec: When it comes to those tests, the tests of knowing stuff, you already have 16 or more years of experience (and grades) under your belt. If the GMAT were yet another one of those tests, it would have no utility. It wouldn’t exist. Instead, the GMAT is precisely the opposite: It’s a test designed to be challenging, and to test skills relevant to business school, while requiring as little concrete knowledge as possible.

If you’re skeptical, go work a few GMAT problems.  Then, when the smoke clears, take an inventory of all the stuff you had to know to solve the problem, as opposed to the thought process itself.  You’ll be surprised by how short the list is, and how elementary the things are.  The challenge isn’t the “what;” it’s the “how.” …Continue reading for the second misconception.
 

How common is it for a student to raise his or her GMAT score 100 points or more, and what is the largest GMAT score increase you’ve personally seen while working at Manhattan Prep?

“We’ve seen such increases from many of our students. I’ve even seen a few increases of more than 300 points, from English learners who made parallel progress on the GMAT and in English itself. I don’t have statistics, but what I can give you is far more important: a list of traits that those successful students have in common.

1) They are flexible and willing to change. They do not cling stubbornly to “preferred” or “textbook” ways of solving problems; instead, they simply collect as many different strategies as possible.

2) They are resilient. When an approach fails, they don’t internalize it as “defeat,” and they don’t keep trying the same things over and over. They just dump the approach that isn’t working, and look for something different. If they come up empty, they simply disengage, guess, and move on.

3) They are balanced. They make time to engage with the GMAT, but they don’t subordinate their entire lives to it. They study three, four, five days a week—not zero, and not seven. They review problems when they’re actually primed to learn; they don’t put in hours just for the sake of putting in hours. If they’re overwhelmed, exhausted, or distressed, they’ll shut the books and hit them another day. In short, they stay sane… Continue reading for more traits of successful students.

Studying for the GMAT? Take our free GMAT practice exam or sign up for a free GMAT trial class running all the time near you, or online. And, be sure to find us on Facebook and Google+,LinkedIn, and follow us on Twitter!

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.

This is the original version of a piece that has since been updated. See Stacey’s latest tips on maximizing the last two weeks before your GMAT. 

What’s the optimal way to spend your last 14 days before the real test? Several students have asked me this question recently, so that’s what we’re going to discuss today! There are two levels to this discussion: building a Game Plan and how to Review. We’ll discuss the former topic in the first half of this article and the latter in the second half.

What is a Game Plan?

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Are You Prepared for B-School Admissions?

Join Manhattan GMAT and three other leaders in the MBA admissions space—mbaMission, Poets & Quants, and MBA Career Coaches—for an invaluable series of free workshops to help you put together a successful MBA application—from your GMAT score to application essays to admissions interviews to post-acceptance internships.

We hope you’ll join us for as many events in this series as you can. Please sign up for each sessions separately via the links below—space is limited.

Session 1: Assessing Your MBA Profile,
GMAT 101: Sections, Question Types & Study Strategies
Monday, September 8 (8:00 – 10:00 PM EDT)
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Session 2: Mastering the MBA Admissions Interview,
Conquering Two 800-Level GMAT Problems
Wednesday, September 10 (8:00 – 10:00 PM EDT)
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Session 3: 9 Rules for Creating Standout B-School Essays,
Hitting 730: How to Get a Harvard-Level GMAT Score
Monday, September 15 (8:00 – 10:00 PM EDT)
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Session 4: 7 Pre-MBA Steps to Your Dream Internship,
Survival Guide: 14 Days to Study for the GMAT
Wednesday, September 17 (8:00 – 10:00 PM EDT)
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We’ve invited mbaMission to share their Business School Essays Analyses as they’re released for the 2014-2015 application season. Here is their analysis for Massachusetts Institute of Technology (Sloan).

The MIT Sloan School of Management bucks conventionality this admissions season and has added to the word count for its application essays—moving from a maximum of 1,000 words to 1,250. The school’s first essay question remains the same as last year’s, but its second essay prompt presents an interesting challenge in that the admissions committee asks you to do exactly what it does not want you to do in reality: write your own recommendation letter. At least in this case, the school is allowing you to do so in the light of day. Thankfully, perhaps, Sloan has dropped its befuddling optional essay, which had invited applicants to share any additional information in any format. Candidates will be content to see clearer directives in the program’s essay questions. As always, our analysis follows…

Essay 1:  The mission of the MIT Sloan School of Management is to develop principled, innovative leaders who improve the world and to generate ideas that advance management practice. Discuss how you will contribute toward advancing the mission based on examples from your past work and activities. (500 words or fewer)
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We’ve invited mbaMission to share their Business School Essays Analyses as they’re released for the 2014-2015 application season. Here is their analysis for University of Michigan (Ross). 

The Ross School of Business at the University of Michigan has refashioned its essay questions, going “smaller” with its requirements, as have several other schools this application season. Ross’s broadly worded essay prompts give you ample breadth—if not an overabundance of words—in which to tell your story. As always, think carefully about what you want to say and the impression you want to make before you start writing, because more opportunity lurks here than you might realize at first.

Essay 1: What are you most proud of professionally and why? What did you learn from that experience? (400 words)
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We’ve invited mbaMission to share their Business School Essays Analyses as they’re released for the 2014-2015 application season. Here is their analysis for University of Pennsylvania (Wharton).  

The Wharton School of the University of Pennsylvania has decreased its number of application essays to just two this year and is giving candidates a whopping 900 words with which to distinguish themselves. We surmise that the influx of application essays can be overwhelming for the school’s overworked admissions officers, who find them somewhat deadening over time. So, by cutting back the program’s application requirements, they are able to stay sharp and still get what they need from you as an applicant. While this change may be helpful on the school’s end, the limitations make your job much harder. Wharton gives you a mostly boilerplate personal statement and a rather Harvard Business School–esque “discuss what you want” style prompt—seemingly not a lot of latitude with which to make an impression, but the key word here is “seemingly.” The smart applicant will make use of Essay 2 in particular to stand out from the pack. Our analysis follows…

This year we require one essay, with a second being optional.  For the second optional essay, we recommend that you to use your best judgment and focus your energy on highlighting new information that we are unable to ascertain from other sections of the application.
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We’ve invited mbaMission to share their Business School Essays Analyses as they’re released for the 2014-2015 application season. Here is their analysis for Columbia Business School. 

For the second year in a row, Columbia Business School (CBS) has kicked off the MBA application season. During an online event with mbaMission, Manhattan Prep and Poets & Quants, CBS’s director of admissions, Christina Shelby, told the audience that the school has added urgency in releasing its questions, because it has to meet the needs of its January-entry (known as J-Term) applicants, whose application deadlines come much sooner (October 8, 2014, versus April 15, 2015). Whatever its rationale for the “early” application release, CBS is basically staying the course with its essay questions, though it has again reduced the allowable character count in its “Twitter-like” goal statement; from 200 characters two years ago, it was cut to 100 last year and now stands at a mere 75. Our analysis follows…

Short Answer Question: What is your immediate post-MBA professional goal? (75 characters maximum)
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We’ve invited mbaMission to share their Business School Essays Analyses as they’re released for the 2014-2015 application season. Here is their analysis for Dartmouth College (Tuck). 

Following what seems to be an emerging trend this season, the Tuck School of Business at Dartmouth College has decreased the number of required applications essays this year from (an already fairly minimal) three to just two 500-word submissions, one of which is a classic career statement, while the other asks candidates to share and reflect on a significant leadership experience. Having just 1,000 words with which to convey meaningful elements of their profile means that applicants will need to be especially judicious in choosing their messages and particularly efficient in their writing to get the most impact from these two rather circumscribed essays. As always, we recommend a thorough brainstorming session before you put pen to paper (or fingers to keyboard) so that your messages are clear, complete and fully on topic.

Please respond fully but concisely to the following essay questions. There are no right or wrong answers. We encourage applicants to limit the length of their responses to 500 words for each essay. Please double-space your responses.

1. Why is an MBA a critical next step toward your short- and long-term career goals? Why is Tuck the best MBA fit for you and your goals and why are you the best fit for Tuck?
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