http://www.businessweek.com/articles/2013-01-16/gmat-tip-defeating-the-romans

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GMAT Tip: Defeating the Romans


Pillaging Rome

Photgraph by Bettmann/Corbis

Pillaging Rome

This tip on improving your GMAT score was provided by Vivian Kerr at Veritas Prep.

Among the more intimidating types of quantitative questions on the GMAT are those that include Roman numerals. Roman numeral questions can be a bit like Integrated Reasoning questions in that you must correctly evaluate all parts of a single question correctly to receive credit. It’s not enough to know that Roman numeral I is correct if you missed the fact that Roman numeral II is also correct. For this reason, students tend to get a little nervous when faced with these questions. The good news is Roman numerals are fairly rare on the GMAT, and when you do see them, they will generally be testing familiar concepts. Let’s take a look at a few questions to see how Roman numerals make easy concepts seem tough.

1. Submarine A and Submarine B are equipped with sonar devices that can operate within a 3,000 yard range. Submarine A remains in place, while Submarine B moves 2,400 yards south from Submarine A. Submarine B then changes course and moves due east, stopping at the maximum range of the sonar devices. In which of the following directions can Submarine B continue to move and still be within the sonar range of Submarine A?

I. North

II. South

III. West

(A) I only

(B) II only

(C) I and II only

(D) II and III only

(E) I and III only

This question seems hard because of the format. But the concepts aren’t difficult at all. Isn’t this just a question of geometry and the properties of circles disguised in a longer word problem in the Roman numeral format? When we draw the diagram, we can see how simple this question actually is. We don’t even have to do any math. The answer must be (E).

Think of the 3,000 as the radius of a circle with a center at Submarine A. The Sub B can continue to travel along the circumference or inside the circle (North and West), but cannot move due south or due east and stay within sonar range.

2. Mr. McCall selects a number that has two digits and is positive. If the number is prime, he assigns that many problems for homework. If the number is not prime, he assigns 8 more problems than the number for homework. If he assigns 97 problems for homework, which of the following could be the number?

I. 89

II. 97

III. 105

(A) I only

(B) I and II only

(C) II only

(D) I and III only

(E) II and III only

O.K., but this one is hard, right? Wrong. The Roman numerals here tell us that the correct answer must be at least one of these three choices, so let’s simply test all three. The correct response is (C). If the number was 97, a prime, then we’d have 97 homework problems, which is confirmed by the question stem. Bingo.

Roman numerals are no harder than other Problem Solving questions. Our unfamiliarity with them makes them scary. Remember, the math itself might be as simple as drawing a diagram.

Vivian Kerr has been teaching and tutoring in the Los Angeles area since 2005. She graduated from the University of Southern California, studied abroad in London, and has worked for several test-prep giants tutoring, writing content, and blogging about all things SAT, ACT, GRE, and GMAT.

For more GMAT advice from Veritas Prep watch “2 Essential Strategies for GMAT Integrated Reasoning Questions”


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