A lot of test takers struggle with the Data Sufficiency questions in the quant section. If you haven’t seen these yet, you will. Data Sufficiency questions turn the tables on a regular question: rather than giving you the information required to solve a question and asking for the answer, Data Sufficiency questions give you a question and ask for the information required to solve that question. It is important to note that in the Data Sufficiency section, you do not actually need to solve the questions–this alone will save you time and stress. In fact, sometimes it will be incredibly difficult and time consuming to solve Data Sufficiency questions without a calculator; again, this doesn’t matter to you, because you don’t need to actually solve them. Your goal in Data Sufficiency questions is to accurately identify which information you would need to solve the question.
Data Sufficiency problems are primarily difficult because they are pretty much unique to the GMAT–I have personally never seen them anywhere else. They force you to look at a problem in a way that you are not used to. Rather, they force you to look at a problem in a way that you are not used to yet. At their core, Data Sufficiency problems are not any harder than other quantitative problems, and, in many ways, are easier because you don’t need to actually solve the problems. You can not only get by, but actually excel on the Data Sufficiency section of the GMAT. In order to improve your score, you will need to (1) develop a comprehensive strategy for approaching Data Sufficiency questions, and, as always (2) practice, practice, practice.
Before I get started on how to approach Data Sufficiency questions, I want to make a quick note about why Data Sufficiency questions are on the GMAT. A lot of people write them off as useless, but understanding why they exist and what they test is crucial to approaching them correctly. Data Sufficiency questions ask you to figure out how to solve a problem efficiently and with minimal information; this mimics the business world decently well. Don’t forget this. To approach the problem correctly, you must understand what it is testing.
Alright, let’s look at the steps to solving Data Sufficiency questions:
Write down A B C D E
A lot of people skip this step. Don’t. Writing down all five answers takes all of 2 seconds, but can easily make the difference between getting a question right or wrong.
Check first statement
Look at the question and analyze whether you can solve it using the first statement provided to you. Do not even look at the second statement yet. Remember, you don’t need to actually solve the question. Just figure out whether you could theoretically find a definite solution using the first statement. Some people find it helpful to work backwards from the question and think about what would more information you would need to solve the problem.
If you can solve the question using the first statement, cross out B, C and E. B is impossible because it states that you can only answer the question with the second statement. C is also impossible, because it states that you need both statements to solve the question and that neither is enough independently. E states that you cannot definitively answer the question, even with both statements, so that is obviously now incorrect. Once you confirm that statement 1 can be used to answer the question, the only options that can still be correct are A (which states that only statement 1 is enough to answer the question) and D (which states that statements 1 and 2 can both be used independently to answer the question).
Check second statement
Next, repeat the same process for the second statement. Whether the first statement provided enough information to answer the question or now, set it aside for now. For this step, focus solely on the second statement. If the first statement allowed you to solve the question, you can solve the question now. If the second statement (by itself) was also correct, then the answer is D, either can be used to solve the question. If the second statement was not enough to answer the question, then your answer is A.
If the first statement is not enough to solve the question and the second statement is, then you are also done. In that case, your answer is B, the second statement by itself allows you to answer the question. If neither statement 1 nor statement 2 allowed you to answer the question independently, the answer to the problem could still be C (both together allow you to answer the question) or E (even together the two statements do not provide enough information to answer the question).
Check both statements together
If statement 1 and/or statement 2 were enough to answer the question, you don’t need to do this step. On the other hand, if neither of the two statements provided enough information, it is absolutely imperative that you do this step. Too often, test takers jump to answering either C or E, without making sure they are picking the correct answer.
For this step, repeat the process that you did for both of the two statements, but this time do it for both of the statements together. If you determine that it is possible to answer the question with both the statements together, the answer is C. Otherwise the answer is E.
Following these steps should provide you a structure to think through Data Sufficiency questions and help them feel more familiar. Like I discuss in more detail in my guide to answering Sentence Correction questions, using a rigorous process to answer questions reduces the chance for human error and allows you to maximize your knowledge and skill. You still need to practice all types of questions to fully master them, but this framework will give you the foundation on which to build your skill with Data Sufficiency questions.