GMAT Tutor: A Little Change in Approach Makes a Big Change in Score

Posted by Jason Shapiro on 11/12/14, 9:30 AM

mackthatchange

I have heard countless times the importance of "just going for it" on a standardized test. Questions are often phrased in a way such that you might have to try two or three different approaches before arriving at the correct answer. The GMAT, however, is a different beast.

When I work with my GMAT tutoring students in Cambridge and Boston, I always advise them to try to spend at least 25% of the time on any question understanding and rephrasing the question, before even looking at the answer choices.

This is particularly true for the Data Sufficiency section of the exam. How can you expect to find the correct answer when you don't even fully know what is being asked? The GMAT is relying on you to keep with the traditional wisdom of just diving in and has designed several different tricks to divert you along the way. If you're not careful, I guarantee you will fall for at least one of them.

Take this example from the Official Guide:

If x, y, and z are positive integers, is x - y odd?

(1) x = z2

(2) y=(z-1)2

Seems easy enough – we need to know if something is odd. Rephrasing a question is not just about understanding it – we understand this one very well – but it’s about being able to express it in a much simpler form. Let’s think about this one. When is x-y odd? Well Odd – Odd = Even, Even – Even = Even, Odd – Even = Odd and Even – Odd = Odd. Therefore, x-y is odd only when one of x and y is even and one is odd. OK, this is a little easier – we can rephrase the question like this:

x, y, z positive integers; is one of x and y even and the other odd?

Now, you can look at the answer choices and see that if one of them is a number squared (same sign as that number), and the other has the same sign as one less than that number, then putting them both together is sufficient. The answer (C) in this case is not as important as the fact that we rephrased the question and made it much easier to understand.

Now let's practice rephrasing a couple more data sufficiency prompts:

1. The hypotenuse of a right triangle is 10 cm. What is the perimeter, in centimeters, of the triangle?

Ugh, so many different complicating issues here. It's a triangle, it's right, it has a hypotenuse, and we need the perimeter. OK, let's just look at the pieces of information and see if those help us clarify. Wrong! We want to really understand this first. So Pythagoras tells us that a2 + b2 = c2, where c is the hypotenuse. Therefore, we know a2 + b2 = 100. And we are looking for the perimeter, which is a + b + c, or a + b + 10. So basically, we have two unknowns, a and b and one equation: a2 + b2 = 100. We need to be able to find a+b. If we can do that, then we have it! Now that we fully understand what is being asked of us, we can dive in.

Let's look at another question now!

2. Is 4x+y = 810?

Another one that seems relatively straightforward, but if you hate dealing with exponents (I sure do), it would be much better to get rid of them. From algebra, we know that 810 = (23)10 = 230 and 4x+y = (22)x+y = 22x+2y. Now we have a new question.

Is 22x+2y = 230? Or said even more simply, is 2x + 2y = 30?
Simplified a bit further: Is x + y = 15?
Now that is much easier.

The GMAT is a test that is specifically designed to trick you, and it is therefore important to try to simplify things every step of the way. You only have 150 minutes to show how well you can do on the quantitative and verbal sections of the GMAT, so make each minute count by fully understanding and rephrasing the question, instead of wasting time going around in circles. If you're struggling, a GMAT tutor can help you figure out what's holding you back, so consider giving Cambridge Coaching a call!

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Tags: GMAT