GMAT Exam (Focus Edition) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Harmonic mean speed

For a trip covering equal distances at speeds a and b, average speed is 2ab/(a+b), not the arithmetic mean (a+b)/2. This is the harmonic mean of the two speeds.

Weighted average formula

Combined mean = (w1·x1 + w2·x2)/(w1 + w2). The result lies between the two group means and closer to the mean of the group with the larger weight.

Combined work rate

If worker A finishes a job in a hours and worker B in b hours, their combined rate is 1/a + 1/b and the time together is ab/(a+b) hours.

Compound interest formula

A = P(1 + r/n)^(nt), where P is principal, r the annual rate as a decimal, n the compounding periods per year, and t the number of years.

Quadratic discriminant

For ax² + bx + c = 0, the discriminant b² − 4ac determines the roots: positive gives two real roots, zero gives one repeated root, negative gives no real roots.

Two-set union formula

The number of elements in A or B equals |A| + |B| − |A ∩ B|. Subtracting the intersection avoids counting elements in both sets twice.

Independent events probability

For independent events A and B, P(A and B) = P(A)·P(B). For any two events, P(A or B) = P(A) + P(B) − P(A and B).

Inequality sign reversal

Multiplying or dividing both sides of an inequality by a negative number reverses the direction of the inequality sign; adding or subtracting does not.

Conclusion versus premise

In a Critical Reasoning argument, the conclusion is the claim the author wants accepted; premises are the evidence offered to support it. Identify the conclusion first.

Necessary assumption

A statement that must be true for the argument's conclusion to follow. Negating it destroys the argument, which is the standard test for a necessary assumption.

Sufficient assumption

A statement that, if added to the premises, guarantees the conclusion. It need not be required by the argument; it only needs to make the conclusion follow.

Weaken the argument

The correct answer typically attacks the unstated assumption linking evidence to conclusion, for example by offering an alternative explanation or showing the evidence is unrepresentative.

Strengthen the argument

The correct answer confirms the assumption connecting evidence to conclusion, for example by ruling out an alternative cause or showing the sample is representative.

Main idea question

Asks for the passage's central claim. The correct answer must cover the whole passage, not one paragraph or a supporting detail, and must match the author's scope.

Inference question

Asks what must be true based on the passage. The answer is supported by the text but not explicitly stated; choices with extreme language are usually incorrect.

EXCEPT question

Four answer choices are supported by the passage and one is not. The task is to find the exception, so eliminate the four supported choices to isolate the answer.

Scope shift

A common wrong-answer pattern in which the choice discusses a topic, group, or time period the passage does not address, making the choice irrelevant to the argument.

Author's attitude

The author's stance toward the subject, such as supportive, critical, or neutral. Distinguish the author's view from views the author reports or criticizes in the passage.

Data Sufficiency task

Decide whether the two statements provide enough information to answer the question, not what the numerical answer is. The five answer choices are fixed and ordered.

Data Sufficiency choice order

Statement 1 alone; statement 2 alone; both together but neither alone; either alone; together still insufficient. Memorize this order because the choices never change.

Testing insufficiency

To show a statement is insufficient, find two different values that satisfy all given constraints but produce different answers to the question. One such pair proves insufficiency.

Multi-Source Reasoning

Questions draw on information spread across multiple tabs. For each answer choice, identify which tab supplies the relevant fact before judging whether the choice is supported.

Table Analysis sorting

Tables can be sorted and filtered by column. Check whether a percentage refers to the whole table or to a subgroup, since sorting changes which rows are visible.

Graphics Interpretation axes

Read axis labels, units, and scales before interpreting a trend. A line can reverse direction within the plotted range, so check the full range, not just the endpoints.

Two-Part Analysis

Two columns must each be answered, and the two correct answers must jointly satisfy the stated relationship. Evaluate each column independently against the constraints.

Percentage change

Percentage change = (new − old)/old × 100. A 20% decrease followed by a 20% increase yields a net 4% decrease, not zero change.

Data Sufficiency with variables

When a question asks for a value, a statement that yields a unique value is sufficient; one that yields multiple possible values is insufficient, even if the values are related.

Yes/no Data Sufficiency

For yes/no questions, a statement is sufficient if it always yields the same answer, whether yes or no. A definite no is sufficient; a sometimes-yes-sometimes-no is not.

Table Analysis percentages

Distinguish row percentages from column percentages. A percentage of a subgroup is not comparable to a percentage of the total unless the subgroup sizes are known.

Graphics Interpretation units

Check whether axis values are in thousands, millions, or percentages, and whether the vertical axis starts at zero. Truncated axes exaggerate apparent differences.

Two-Part relationship constraint

The two selected answers must satisfy any equation or condition stated in the prompt, such as one value being twice the other or their sum equaling a given total.

Multi-Source conflicting data

When tabs present data from different periods or sources, check whether they are directly comparable. A choice that mixes incompatible sources is usually incorrect.