# 3 Things the GMAT Testmakers Don’t Want You to Know

As I discussed in my last entry on The Art of War and success on the GMAT, the makers of the GMAT have only a few ways to attack you in battle.  They also have a few things that keep a figurative arm tied behind their back.  These limitations are what you can, and should, exploit to your advantage.  However, it may still not be clear who exactly you’re dealing with.  And as you remember, knowing thy enemy (and thyself) is key to a great score.

With that in mind, there are a few things to consider above and beyond the mechanics of the battle.  What advantages do the GMAT testmakers have that they would rather you didn’t know?  I can think of three.  Today, the first:

1.     They Can Do These Problems In Their Heads

This applies largely to the Quant section.  Sound surprising?  It’s strikingly true, but don’t be impressed yet.  The reason the testmakers can do most quant problems all in their heads is that the questions are actually tailored to some fundamental math property or a unique insight that, once uncovered, helps unpack them in a simple way.  Think about it: the way many quant problems are written is by reverse engineering them around some special relationship or property.  Take the following algebra problem:

In the infinite sequence a1, a2, a3, … an where an= n2, what is a1,323 – a1,322 ?

Without carefully examining it, it seems somewhat time consuming.  You could shortcut by looking for the units digit, right?  Sure, but odds are there are three answer choices with the correct units digit of 5.  You could of course take the long route, square 1,323 and 1,322 and subtract the two.  On paper.  But the test maker is tuned into the fact that the difference of consecutive squares increases in a pattern: by 2 for each value of n.  For instance, squaring 0,1,2,3,4… yields 0,1,4,9,16…  The difference between each consecutive value in the sequence is 1,3,5,7… etc.   There’s a pattern.  The latest difference of consecutive squares is simply one less than double the latest value of n.  Therefore, one less than double 1,323 is 2,645. Problem solved!

Another way to think about the mathematical pattern is as the sum of the two consecutive bases – the differences of 1,3,5,7 are also the sums of 0+1, 1+2, 2+3, 3+4 etc.  Similarly, 1,323 + 1,322 = 2,645.

By having drilled as many of the fundamental properties of Arithmetic, Algebra, Geometry, and more, you’ll begin to recognize the quick insight the test maker is running on when he or she formulated the question in his or her mind.  Remember, the test makers are enjoying the game of creating problems that can be solved entirely up top.  They just don’t want you to know it.

Stay tuned for the Part II of Things the GMAT Testmakers Don’t Want You to Know, coming soon!

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Joseph Dise has been teaching GMAT preparation for Veritas Prep for the last 4 years in Paris and New York City.