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GMAT Club

GMAT Tip: Playing To Win

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Admit it: You had at least a class or two in school for which you thrived on partial credit – you wouldn’t get many answers correct, but with participation points and partial credit for doing most of the steps correctly you could comfortably claim your B.   So on a test like the GMAT, which is all-or-nothing with no potential for partial credit, the prospect of having to be 100% correct on any given problem is a little daunting.

Where the GMAT can make this even more difficult is by subtle wordplay that allows for you to do all the work correctly on a problem, but by missing or tweaking your read of just one word in the question coming up with a completely different incorrect answer.  As such, attention to detail on the GMAT is crucial – you need to learn to spot those ever-critical words that, on a dime, can change the answer from B to D.

Perhaps a video will illuminate this concept best, and in honor of Veritas Prep’s many game show veteran instructors, this may be the most appropriate:

https://www.youtube.com/watch?v=m5CfU316M0g&feature=player_embedded

Chris Farley’s character here makes the classic error of missing an ever-important word:  “I thought the concierge meant to go SEE a game show, not BE ON a game show.  Big mistake!”  This is a game show pitfall that Los Angeles GMAT instructor (and Jeopardy! champion) George Yates knew well to avoid; that Los Angeles GMAT tutor Travis Morgan…well, you will see this fall on NBC; and that New York City GMAT Instructor Dave Halliday, well, learned the hard way in the waning minutes of his w0uld-be-champion Jeopardy! run, missing a key word on Final Jeopardy! and incorrectly answering a question to which he knew the correct answer, losing his lead and the game in the process.

Dave rallied to avoid that mistake on the GMAT, however, and all of these elite GMAT instructors want you to do the same. You  have to pay attention to key words on the GMAT.  Consider this example:

If a positive even number n is not divisible by 3 or 4, then the product (n + 6)(n + 8)(n + 10) must be divisible by which of the following?

I. 24

II. 32

III. 96

A. None
B. I only
C. II only
D. I and II only
E. I, II, and III

This question offers several constraints for the possible values of n, and missing any one of those key traits will likely cost you the question.  N must be:

  • Positive
  • Even
  • Not divisible by 3
  • Not divisible by 4

As this question was discussed by aspiring MBA students in a forum  thread earlier this week, the most common reason for someone to miss it was that they missed that small word “even”; they’d plug in a number like 1 or 5 for n – numbers that ARE NOT possible given the constraints – and incorrectly believe that the answer is E.  In actuality, however, these constraints taken together mean that the only possible values for n are numbers like:

2, 10, 14, 22, 34…

And for these numbers, the product of (n+6)(n+8)(n+10) is divisible by all of the above.  We are  assured that, if n is even but not divisible by 4, then n + 6 and n + 10 WILL BE divisible by 4 (try it: 2, 6, 10, 14…all of these numbers are even but not divisible by 4; add 6 and you get 8, 12, 16, 20 —> all divisible by 4).  So the product will give us:

(n + 6)(n + 8)(n + 10)

Divisible by 4 * Even * Divisible by 4

Providing prime factors of (at minimum):

(2*2)(2)(2*2) –> the product must be divisible by 2^5.

And because we have three consecutive even integers, exactly one will be divisible by 3 (try it:  2, 4, 6, 8, 10, 12, 14, 16, 18… – every third value is divisible by 3).

So we know that the product is divisible by 3*2^5, and to be divisible by I, II, and III we need:

24: 3*2^3 (check!)

32: 2^5 (check!)

96: 3*2^5 (check!)

Regardless of how comfortable you feel with prime factorization and number properties, however, if you miss the term “even” or “not” (in “not divisible by 4″) you’ll get this question wrong.  The GMAT requires you to pay attention to those details, and to have that extra sense for which words are likely to be gamechangers – words like:

Definitions of numbers:

Even, Odd, Nonzero, Nonnegative, Integer, Positive, etc.

Parameters:

All, Some, None, Not, Not All, etc.

Author’s intent:

However, Also, Therefore, etc.

As you make mistakes – and rest assured you WILL make mistakes – in practice, note the subtle wordplay that causes you to do so, and heighten your awareness for those terms.  Unlike Chris Farley, you can recover from GMAT mistakes with all ten fingers intact (this will help with the AWA essay), but you would be wise to learn from them.  The devil is in the details, and the GMAT loves to embed important details in what may look like subtle wordplay. Word to the wise: watch those words carefully.

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