About GMAT Data Sufficiency
The data sufficiency question type is unique to the GMAT. It is not found on the SAT, ACT, or any other major standardized test. Data sufficiency questions are designed to test your ability to analyze data and determine what information is necessary in solving a problem. Each data sufficiency problem contains a question and two accompanying statements. Your task is to determine whether the statements provide sufficient information for answering the question.
The official directions for data sufficiency problems are as follows:
Each data sufficiency problem consists of a question and two statements, labeled (1) and (2), that give data. 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 the data given in the statements are sufficient for answering the questions.1
If you are new to the GMAT, do not be dismayed if this question type seems confusing. It takes most students 10-20 practice questions before they understand how the question format works. First, familiarize yourself with what is meant by sufficiency. Second, understand the two main types of data sufficiency questions. Third, work practice questions, starting with the easiest problems and working your way to those that are more difficult.
The logic of the answer choices is arranged as follows: