GMAT Exam (Focus Edition) cheat sheet

Problem Solving questions have five answer choices; no Data Sufficiency on the Focus Edition.

Average speed for a round trip over equal distances is the harmonic mean: 2ab/(a+b), not (a+b)/2.

For weighted averages, the combined mean = (w1·x1 + w2·x2)/(w1 + w2); the result lies closer to the group with the larger weight.

Work rate: combined rate = sum of individual rates; time together = 1/(1/a + 1/b) = ab/(a+b).

Compound interest: A = P(1 + r/n)^(nt); simple interest: A = P(1 + rt).

Probability of A or B = P(A) + P(B) − P(A and B); independent events: P(A and B) = P(A)·P(B).

Overlapping sets: |A ∪ B| = |A| + |B| − |A ∩ B|; for three sets subtract pairwise intersections and add back the triple intersection.

A quadratic ax² + bx + c = 0 has discriminant b² − 4ac; two real roots if positive, one if zero, none if negative.

Inequalities: multiplying or dividing both sides by a negative number reverses the inequality sign.

Critical Reasoning: the conclusion is the claim the argument is trying to establish; premises are evidence offered for it.

To weaken an argument, attack the assumption linking evidence to conclusion; to strengthen, confirm that assumption.

A necessary assumption must be true for the conclusion to follow; a sufficient assumption guarantees the conclusion.

Reading Comprehension: the main idea must cover the entire passage, not just one paragraph or an example.

For inference questions, the correct answer is supported by the passage but not explicitly stated; extreme wording is usually wrong.

For 'EXCEPT' questions, four choices are supported and one is not; eliminate the four supported choices.

Author's attitude questions: distinguish the author's view from views the author merely reports or criticizes.

Scope shifts are a common wrong-answer pattern: the choice discusses a topic the passage does not address.

Data Sufficiency: determine whether the data are sufficient, not the numerical answer; the five choices are fixed.

Data Sufficiency choice order: (1) statement 1 alone, (2) statement 2 alone, (3) both together but neither alone, (4) either alone, (5) together still insufficient.

In Data Sufficiency, test values that satisfy the constraints but produce different results to prove insufficiency.

Multi-Source Reasoning: information is spread across tabs; check which tab each answer choice depends on.

Table Analysis: sorting and filtering are available; verify whether a percentage is of the total or of a subgroup.

Graphics Interpretation: read axis units and scales carefully; a trend can reverse direction within the plotted range.

Two-Part Analysis: each column must be evaluated independently; the two correct answers must satisfy the stated relationship.

Percentage change = (new − old)/old × 100; a 20% decrease followed by a 20% increase yields a net 4% decrease.