GMAT Tip of the Week: The Greatest Trick The Devil Ever Pulled

GMAT PrepHappy Halloween Weekend!  As we prepare for Devil’s Night tomorrow, it seems only fitting that we take a moment to reflect on lessons that the devil can teach us about the devilishly-clever GMAT.  While he’s not going down to Georgia, wearing a blue dress, and baking food cake, the devil is pulling tricks (with no treats) – he is, after all pure evil.  And to quote the knowledgeable Keyser Soze, the greatest trick the devil ever pulled was convincing the world that he didn’t exist.  Which is to say that evil is at its worst when you least expect it.

The same is true of the GMAT, on which the devilishly-clever authors are often able to pull that same trick – adding difficulty without you even knowing that it exists.

Consider the question:

What is the value of x?

1) 4x – 6y = 18

2) x = 3(y+3)/2

On the surface, this question looks to be fairly easy.  There are two variables, so you would need two equations to be able to solve for either variable.  Neither statement alone will be sufficient, but both together should do the  trick, right?
Wrong.  The difficulty here is understated – the two equations look to be quite different, but in fact they are the same.  Take the first:

4x – 6y = 18

And manipulate it a bit:

2x – 3y = 9  (divide both sides by 2)

2x = 3y + 9 (add 3y to both sides)

2x = 3(y+3) (factor the 3 out of both terms on the right)

x = 3(y+3)/2 (divide both sides by 2)

In fact, both statements together only give us one equation, and that equation is not sufficient to determine the value of x.  The correct answer is then E (for evil?).

Note this about easy-looking GMAT questions:

1) Often they look easy because you’re missing the “GMAT convinced you it didn’t exist” difficulty.  DO NOT let an easy-looking question make you think that you’re performing poorly.

2) When questions do look easy, check to see that you’re not missing some hidden difficulty.  On Data Sufficiency questions like this, for example, rearranging the algebra in a question can help you get more mileage out of a statement.  Is it actually sufficient on its own?  Does it merely replicate information already given?  Are you making assumptions that you can’t (e.g. “x is an integer” or “x is positive”)?  Or should you be making assumptions (if x represents a number of people, it has to be an integer) that you aren’t?

On the GMAT, the devil is in the details – what may look easy could actually be difficult if you pause to look for that key word or concept that the authors are using to devilishly hide their difficulty.  Know that the devil’s greatest trick is convincing you it’s not even there.  Study accordingly, and give the GMAT hell!

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