Data Sufficiency on the GMAT Focus: a decision procedure

Data Sufficiency rewards a habit that school math never teaches: deciding without finishing. The question asks whether the information is enough, and candidates who solve every problem to the end often run out of time and still pick the wrong letter. This guide gives you a decision procedure you can run on every Data Sufficiency question in the GMAT Focus Data Insights section, plus the number-testing habit that makes the procedure fast.

What the question looks like

A Data Sufficiency question has three parts: a question, statement (1), and statement (2). The five answer choices never change. In our own shorthand:

• A: statement (1) works alone, and statement (2) does not.
• B: statement (2) works alone, and statement (1) does not.
• C: neither works alone, but the two work together.
• D: each statement works alone.
• E: the two fail even together.

On the GMAT Focus Edition the format lives in Data Insights, not in Quant. The prompts range from algebra and number properties to real-world scenarios and pure logic, and the decision logic stays the same across all of them.

Step 1: Classify the question

Every Data Sufficiency question is either a value question or a yes-or-no question. A value question asks for a number: what is x, how many units did the plant ship, what is the average. A statement is sufficient only if it pins the value down to exactly one number. A yes-or-no question asks whether something is true: is x positive, did revenue exceed cost, is n divisible by 6. A statement is sufficient if it forces a single answer, and that answer can be No. Write V or Y/N at the top of your scratch work before you read the statements; the classification decides what sufficient means for the rest of the question.

Step 2: Rephrase what you need

Translate the question into the smallest fact that would settle it. If the question asks for the value of 3x + 6, you need x and nothing more. If it asks whether an integer is divisible by 6, you need to know whether it is divisible by both 2 and 3. If it asks whether a company made a profit, you need the sign of revenue minus cost, not either number by itself. The rephrase takes ten seconds and prevents the most expensive mistake in the format: judging a statement against the wrong target.

Step 3: Test statement (1) alone and write AD or BCE

Read statement (1) on its own. Ask one question: with this fact and the information in the stem, could I produce exactly one answer? If yes, write AD on your paper; the answer is now A or D. If no, write BCE; the answer is now B, C, or E. You have eliminated two or three choices with a single judgment, and the letters on your paper keep you from drifting.

Do not compute the answer unless computing is the fastest way to see whether one exists. Often a glance at the structure settles it: one linear equation in one unknown gives one value; one equation in two unknowns usually does not; a statement that only restates the stem adds nothing.

Step 4: Reset, then test statement (2) alone

Cover statement (1), physically or mentally, and read statement (2) as if you had never seen the first one. Under time pressure people skip this reset, and skipping it produces a classic wrong answer: choosing B or D because statement (2) looked sufficient while statement (1) was still in your head. If you wrote AD after step 3 and statement (2) also works alone, the answer is D; if it fails alone, the answer is A. If you wrote BCE and statement (2) works alone, the answer is B. If it fails, move to step 5.

Step 5: Combine only when both fail

You reach this step only on the BCE branch with statement (2) insufficient. Now use both statements together. If the combination gives exactly one answer, choose C. If it still allows two answers, choose E. Candidates who combine the statements before testing each one alone lose the A, B, and D answers, because combined information often looks sufficient even when one statement alone would do.

How to test numbers without wasting time

When a statement is algebraic or about number properties, the fastest test is to try to produce two different answers to the question. If you can, the statement is insufficient; if every legal case gives the same answer, it is sufficient. The trick is choosing cases that are likely to disagree:

• Zero, one, and a negative number, because they break rules that hold for positive integers.
• A fraction between 0 and 1, because squaring it makes it smaller.
• An even and an odd value when the question turns on divisibility.
• The smallest and greatest values the statement allows when the question concerns a range.

Stop as soon as two cases disagree. One conflicting pair proves insufficiency; you gain nothing from a third case.

Yes-or-no questions: a definite No is sufficient

Example: suppose a question asks whether x is greater than 10, and a statement tells you that x is negative. Every value the statement allows gives the same answer, No, so the statement is sufficient. Many candidates read a No as a failure and mark the statement insufficient, which costs them the question. On a yes-or-no question, a statement fails only when it allows both a Yes case and a No case.

The GMAT Focus twist: real-world sufficiency

Some Data Insights prompts describe a situation, such as a store deciding whether a promotion raised profit, and the statements offer facts a manager might collect. The procedure does not change. Classify, rephrase the decision into the quantity that settles it, and judge each statement alone. The temptation is to reason like a manager and accept plausible information as decisive. Sufficiency sets a stricter bar than plausibility: a statement counts only if it forces one answer.

The traps the procedure blocks

• Solving to the end. You need to know whether an answer exists, not what it is. Step 3 asks a yes-or-no question about existence.
• Carrying statement (1) into statement (2). Step 4 resets.
• Assuming integers or positives. Unless the stem says integer or positive, test a fraction and a negative.
• Counting equations instead of checking them. Two equations in two unknowns fail when one is a multiple of the other, and a single equation can settle a question that asks only for a combination, such as x + y.
• Treating a definite No as insufficient. On a yes-or-no question, a forced No settles the question.
• Picking C out of relief. When both statements together obviously work, check that neither works alone before you choose C.

Pacing

A practiced Data Sufficiency question takes 90 seconds to two minutes, and the procedure makes that possible: each step ends with a decision and a letter on the page. If you pass three minutes, the question has probably pulled you into solving. Write the most likely letter from the branch you reached, bookmark the question, and move on. Question Review & Edit lets you come back to it and change up to three answers per section if time remains.

Run the procedure on every question until you no longer have to think about the steps. GMAX holds Data Sufficiency questions across the whole difficulty range and shows an explanation after every answer, and the free plan gives you five questions a day.