INTRODUCTION DATA SUFFICIENCY
Most people have much more difficulty with the Data Sufficiency problems than with the Standard GMAT Math problems. However, the mathematical knowledge and skill required to solve Data Sufficiency problems is no greater than that required to solve standard math problems. What makes Data Sufficiency problems appear harder at first is the complicated directions. But once you become familiar with the directions, you’ll find these problems no harder than standard math problems. In fact, people usually become proficient more quickly on Data Sufficiency problems.
THE DIRECTIONS
The directions for GMAT Data Sufficiency questions are rather complicated. Before reading any further, take some time to learn the directions cold. Some of the wording in the directions below has been changed from the GMAT to make it clearer. You should never have to look at the instructions during the GMAT.
Directions: Each of the following Data Sufficiency problems contains a question followed by two statements, numbered (1) and (2). You need not solve the problem; rather you must decide whether the information given is sufficient to solve the problem.
The correct answer to a question is
A if statement (1) ALONE is sufficient to answer the question but statement (2) alone is not sufficient;
B if statement (2) ALONE is sufficient to answer the question but statement (1) alone is not sufficient;
C if the two statements TAKEN TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient;
D if EACH statement ALONE is sufficient to answer the question;
E if the two statements TAKEN TOGETHER are still NOT sufficient to answer the question.
Numbers: Only real numbers are used. That is, there are no complex numbers.
Drawings: The drawings are drawn to scale according to the information given in the question, but may conflict with the information given in statements (1) and (2).
You can assume that a line that appears straight is straight and that angle measures cannot be zero.
You can assume that the relative positions of points, angles, and objects are as shown.
All drawings lie in a plane unless stated otherwise.
Example:
In triangle ABC above, what is the value of y?
(1) AB = AC
(2) x = 30
Explanation: By statement (1), triangle ABC is isosceles. Hence, its base angles are equal: y = z. Since the angle sum of a triangle is 180 degrees, we get x + y + z = 180. Replacing z with y in this equation and then simplifying yields x + 2y = 180. Since statement (1) does not give a value for x, we cannot determine the value of y from statement (1) alone. By statement (2), x = 30. Hence, x + y + z = 180 becomes 30 + y + z = 180, or y + z = 150. Since statement (2) does not give a value for z, we cannot determine the value of y from statement (2) alone. However, using both statements in combination, we can find both x and z and therefore y. Hence, the answer is C.
Notice in the above example that the triangle appears to be a right triangle. However, that cannot be assumed: angle A may be 89 degrees or 91 degrees, we can’t tell from the drawing. You must be very careful not to assume any more than what is explicitly given in a Data Sufficiency problem.
Are you ready for the GMAT?
With our comprehensive book, you can be sure!
Although the GMAT is difficult, it is very learnable. GMAT Prep Course presents a thorough analysis of the GMAT and introduces numerous analytic techniques that will help you immensely, not only on the GMAT but in business school as well.
Nova’s GMAT Prep Course is the best GMAT prep book available, providing the equivalent of a 50-hour, 6-week course. This comprehensive test prep book provides twenty-two chapters of review material and hundreds of GMAT-style practice problems and examples. Plus, we’ll take you inside the heads of the test question writers to help you understand and outsmart the GMAT question mentality.
Dedicated preparation with Nova’s GMAT Prep Course has been shown to significantly increase GMAT scores. If you want to get your best score on the GMAT, you can’t afford not to try it!
Features:
- Math: Twenty-two chapters provide comprehensive review of GMAT math.
- Logical Reasoning: Discover the underlying simplicity of these problems and learn the tactics the GMAT writers use to obfuscate the answers.
- Reading Comprehension: Develop the ability to spot places from which questions are likely to be drawn as you read a GMAT passage (pivotal words, counter-premises, etc.).
- Writing Assessment: Learn how to get top scores on your Analysis of Issue and Analysis of Argument essays.
- Mentor Exercises: These exercises provide hints, insight, and partial solutions to ease your transition from seeing GMAT problems solved to solving them on your own.
- Test Mentality: 15% of this book is dedicated to training you to think like a test writer to help you spot red herrings AND correct answers.
- Hundreds of GMAT-style questions with detailed solutions!
- Study plan suggestions based on the amount of time you have before the exam
Testimonials:
“Far and away the best book…After doing all drills in Nova, the commonly considered difficult practice questions in Kaplan were almost a joke. I would recommend to anyone this book.”
“I got a 690 on the GMAT using only this book, and studying sporadically for a few weeks leading up to the test.”
“I am very happy to say that at the GMAT exam, for which I studied with this book, I received 710 points.”
“I am a Professor of English, and… I make it my business to find books and use them to help students get into graduate school. I have found the Nova book complete in every aspect… Furthermore, the student should have a complete understanding of the math and sentence correction portions upon completion of the course. Without unnecessary rhetoric, the text is exact, with comprehensive yet concise answers, in the math and verbal sections.This is definitely a three year crash course in a several month program.”
Pages 624
Price: $39.95
ISBN: 1889057401
Purchase GMAT Data Sufficiency Prep Course (Domestic) (printed book) (Free shipping within the United States.) (We do not ship outside of the United States.)
GMAT Data Sufficiency Prep Course eBook ($19.95)
ELIMINATION
GMAT Data Sufficiency questions provide fertile ground for elimination. In fact, it is rare that you won’t be able to eliminate some answer-choices. Remember, if you can eliminate at least one answer choice, the odds of gaining points by guessing are in your favor.
The following table summarizes how elimination functions with Data Sufficiency problems.
| Statement | Choices Eliminated |
| (1) is sufficient | B, C, E |
| (1) is not sufficient | A, D |
| (2) is sufficient | A, C, E |
| (2) is not sufficient | B, D |
| (1) is not sufficient and (2) is not sufficient | A, B, D |
Example 1: What is the 1st term in sequence S?
(1) The 3rd term of S is 4.
(2) The 2nd term of S is three times the 1st, and the 3rd term is four times the 2nd.
(1) is no help in finding the first term of S. For example, the following sequences each have 4 as their third term, yet they have different first terms:
0, 2, 4
-4, 0, 4
This eliminates choices A and D. Now, even if we are unable to solve this problem, we have significantly increased our chances of guessing correctly–from 1 in 5 to 1 in 3.
Turning to (2), we completely ignore the information in (1). Although (2) contains a lot of information, it also is not sufficient. For example, the following sequences each satisfy (2), yet they have different first terms:
1, 3, 12
3, 9, 36
This eliminates B, and our chances of guessing correctly have increased to 1 in 2.
Next, we consider (1) and (2) together. From (1), we know “the 3rd term of S is 4.” From (2), we know “the 3rd term is four times the 2nd.” This is equivalent to saying the 2nd term is 1/4 the 3rd term: (1/4)4 = 1. Further, from (2), we know “the 2nd term is three times the 1st.” This is equivalent to saying the 1st term is 1/3 the 2nd term: (1/3)1 = 1/3. Hence, the first term of the sequence is fully determined: 1/3, 1, 4. The answer is C.
Example 2: In the figure above, what is the area of the triangle?
(1) 
(2) x = 90
Recall that a triangle is a right triangle if and only if the square of the longest side is equal to the sum of the squares of the shorter sides (Pythagorean Theorem). Hence, (1) implies that the triangle is a right triangle. So the area of the triangle is (6)(8)/2. Note, there is no need to calculate the area–we just need to know that the area can be calculated. Hence, the answer is either A or D.
Turning to (2), we see immediately that we have a right triangle. Hence, again the area can be calculated. The answer is D.
If you like this material, you’ll love the course!
This interactive, comprehensive self-study course presents the equivalent of over 600 pages of printed material, including hundreds of GMAT examples, problems, videos, and feedback from GMAT experts to your questions. In addition, the powerful learning engine StudyDesk increases your learning efficiency by monitoring your progress and directing you to areas where you need further study. All for only $49.95!. Click the link above for more information or call 1-310-275-3513.
Course Features:
- Ask Questions! Our instructors monitor StudyDesk to answer your questions. StudyDesk also records the step where you make a mistake or ask a question. This is just one of many powerful educational tools in StudyDesk.
- Highly Interactive: You can take notes, view solutions, and view reports, etc.
- Videos: More than 500 videos guide you through the concepts and examples.
- Versatile: You can access the course from any computer at any time.
- Statistics: Your performance on the exercises is saved and you may review your performance and check solutions at any time. You can also check your ranking based on all students taking the course. How cool is that!
- Guarantee: If, at the end of the course, you do not feel sufficiently prepared for the test, you may repeat the course for free — with full access to our instructors.
Example 3: Is p < q ?
(1) p/3 < q/3
(2) -p + x > -q + x
Multiplying both sides of p/3 < q/3 by 3 yields p < q.
Hence, (1) is sufficient. As to (2), subtract x from both sides of -p + x > -q + x, which yields
-p > -q
Multiplying both sides of this inequality by -1, and recalling that multiplying both sides of an inequality by a negative number reverses the inequality, yields p < q.
Hence, (2) is also sufficient. The answer is D.
GMAT Prep Course Software
 |
Don’t waste hundreds, even thousands of dollars paying a test prep company to prepare you for the GMAT. Now, you can get the same preparation in a downloadable software program for less than a fraction of the cost!
Nova’s GMAT Prep Course Software is the best in GMAT prep. First, it takes you step-by-step through GMAT math and verbal content reviews as well as the “mentality” behind various GMAT questions. Then, take your time to do as many GMAT-style practice problems as you need! Our software contains hundreds of practice problems, all with detailed explanations to help you to the right answer. Finally, take the 4 scored GMAT practice exams, and watch your score climb!
Features:
- Mentor Mode: In Mentor Mode, you are immediately told whether you answered a GMAT problem correctly, and you can view a solution of the problem.
- Test Mode: In Test Mode, you can take a GMAT test timed and scored by the program.
- Math: Seventeen Lessons, with exercises, (see screen shot below) provide comprehensive review of GMAT math. Also includes a summary of GMAT math properties.
- Reading Comprehension: Develop the ability to spot places from which questions are likely to be drawn as you read a GMAT passage (pivotal words, counter-premises, etc.).
- Logical Reasoning: Discover the underlying simplicity of these GMAT problems and learn to recognize common answer patterns.
- Data Sufficiency: Learn how to easily master these dreaded GMAT problems.
This comprehensive program contains detailed solutions to hundreds of GMAT questions.
Get the GMAT Prep Course software, downloadable now for $29.95.
To order and download the software, click the links below:
