GMAT Quantitative Data Sufficiency Basics
The GMAT data sufficiency questions are one of two types on the GMAT Quantitative section. The other type is problem-solving. The data sufficiency questions account for just 13 – 14 out of the 37 questions, but they'll take a little bit longer and are a bit tougher, from most people's perspective, than the problem-solving questions. So, here's what you need to know:
Data Sufficiency Format
These are multiple-choice questions, but unlike the problem-solving questions, the answer choices will always be the same. Your job with data sufficiency questions is to determine if there is enough information available to answer the question presented.
You'll see these directions before your first data sufficiency question. If you need to see them again when you're taking the test, you can just click on the "Help" icon.
Directions: This problem consists of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of counterclockwise), you must indicate whether:
- statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked;
- statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked;
- BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient;
- EACH statement ALONE is sufficient to answer the question asked;
- statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.
Numbers: All numbers used are real numbers.
Figures: A figure accompanying a data sufficiency problem will conform to the information given in the question, but will not necessarily conform to the additional information in statements (1 and 2).
Lines shown as straight can be assumed to be straight and lines that appear jagged can also be assumed to be straight. You may assume that positions of points, angles, regions, etc., exist in the order shown and that angle measures are greater than zero. All figures lie in a plane unless otherwise indicated.
Data Sufficiency Examples
1. If N, C, and D are positive integers, what is the remainder when D is divided by C?
1. If D+1 is divided by C+1, the remainder is 5.
2. If ND+NC is divided by CN, the remainder is 5.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statement (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data are needed.
2. Is (-x) a negative number?
1. 4x2 – 8x > (2x)2 – 7x
2. x + 2 > 0
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statement (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data are needed.
