One of the key things to remember with circles is that once you know one piece of information, you know everything about the circle itself. Additional angles and lengths inside are not always so simple, but it is possible to convert circumferences to areas, to radii and diameters without intermediate steps. This will save you time in Data Sufficiency questions.

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Last week, we tackled two GMATPrep® questions; if you missed that article, go read it before continuing with this one. Make sure you try the two sample problems and take the time to master the concepts before you try the super-hard question below.

Okay, this sample problem is from our own archives. Set your timer for 2 minutes…. and… GO!

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In Part I of this series, I talked about approaching wordy GMAT questions as a businessperson would--by carefully reading these questions the first time around in order to absorb all information. The following GMAT problem has inspired me to expand this approach questions to include the actual process of decision-making:

A square countertop has a square tile inlay in the center, leaving an untiled strip of uniform width around the tile. If the ratio of the tiled area to the untiled area is 25 to 39, which of the following could be the width, in inches, of the strip?

I. 1
II. 3
III. 4

a. I only
b. II only
c. I and II only
d. I and III only
e. I, II, and III

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To start off, let’s quickly review the essentials. These are formulas/concepts you must know:

1. a² + b² = c², but only when a right triangle. If you don’t know it’s a right triangle, Pythagorean theorem does not apply!
2. Common special right triangles include 3-4-5, 5-12-13, 8-15-17, 7-24-25 (and their multiples.)
3. 45-45-90 triangles are ALWAYS in the ratio 1:1:√2
4. 30-60-90 triangle are ALWAYS in the ratio 1:√3:2
5. Angles and opposite sides are in the same relative size order, but are NOT proportional.

Let’s continue with a standard diagram in which we have an equilateral triangle inscribed in a circle, which is inscribed in a square.

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The following book review was written by Dana Jinaru.  Dana is currently a finance student in Europe and also serves as a moderator for Beat The GMAT.  On May 13, 2009 she scored a 770 on the GMAT.

Here is Dana’s analysis of The Princeton Review Cracking The GMAT book.

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There are several number properties that GMAT test takers need to know / memorize.  A lot of these seem simple at first glance; however, the GMAT is very good at finding ways to make straightforward concepts difficult.  Additionally, there are number property concepts that are not as straightforward as others.  One of the more difficult concepts is exponent properties.

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For many, the GMAT study experience will take several months. These months take the form of figuring out what is on the test, doing many practice problems, perhaps taking a review class, taking practice tests and then mentally preparing for the tests in the final few weeks. This article suggests some pre-test routines and gives an idea of what people should be expecting and doing in the months leading up to their test.

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In this series, we will cover many types of geometric scenarios encountered on the GMAT. A basic knowledge of simple formulas (area, perimeter, etc.) is essential, but there are numerous shortcuts to geometry questions that will save you time. Today, we’ll explore circles inscribed in squares.

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Over the years, GMAT instructors will tell you that they hear common refrains from our students and friends.  As I think about the past years of teaching, I have compiled a list of three of the most common pitfalls my students at Kaplan and personal friends have experienced while they are prepping for the GMAT.

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I read A LOT of GMAT essays. Alex Sarlin and I read every single essay sent in by every single Knewton student. More and more are coming in every day. We usually offer words of encouragement followed by a few points of constructive critique -- don't use first-person pronouns in the intro, don't pay too much deference to the other side of the argument, and so forth.

But last week we received an essay that was so good, we asked asked its author to let us share it with the world. So here it is, followed by a breakdown of why we like it so much.

Reprinted with Robbie M's permission (thanks Robbie!).

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Even though Data Sufficiency questions test the same math content as Problem Solving questions, most GMAT students find that they can’t use the same strategies on both question types. One of the common errors students make in their approach to Data Sufficiency questions is jumping to the two statements without analyzing the question first and figuring out what information is missing. You wouldn’t start hunting for a jigsaw puzzle piece without first looking at the shape of the hole you’re trying to fill, would you? Most Data Sufficiency questions can be simplified with the Pieces of the Puzzle approach, and some would be nearly impossible to solve without it.

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The following book review was written by Dana Jinaru.  Dana is currently a finance student in Europe and also serves as a moderator for Beat The GMAT.  On May 13, 2009 she scored a 770 on the GMAT.

Here is Dana’s analysis of the Manhattan GMAT Sentence Correction guide.

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The following book review was written by Dana Jinaru.  Dana is currently a finance student in Europe and also serves as a moderator for Beat The GMAT.  On May 13, 2009 she scored a 770 on the GMAT.

Here is Dana’s analysis of PowerScore’s GMAT Critical Reasoning Bible.

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The answer to yesterday's question.  Try the problem first if you haven't done so already and click more to see if you got the answer right.

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