Concepts

The GMAT Concept Atlas

That is a different question, and it is the one that decides scores. Almost everyone sitting the exam can define a percentage. Far fewer can tell, inside two minutes, which of two plausible numbers the question wants the change measured against — and that is what the question is testing.

So each page here is organised around the decision the concept forces:

• what the GMAT actually tests, as distinct from what the topic contains
• the forms the idea takes when it is disguised
• the mistakes that follow, mapped to their named traps
• what mastery looks like, stated as things you can do rather than things you know
• one original example, and one question to try

Quantitative Reasoning

• Percentages — the reference base is the whole test
• Data Sufficiency — certainty is the target, not a value

Verbal Reasoning

• Assumptions — the bridge the argument needs, not the fact that helps
• Causal Reasoning — direction, alternatives and what would change your mind

Data Insights

• Graphics Interpretation — read the axes before you read the shape

What is not here, deliberately

There is no page defining what a percentage is, and there will not be one. If a definition is the thing you are missing, a textbook or a two-minute video will serve you better and faster than we can.

There is also no page for every subskill. A concept earns a page when the GMAT tests it as a decision — when there is a recurring choice the question forces and a recurring way that choice goes wrong. Splitting that into eight micro-pages would make each one thinner and none of them easier to find.

Concept gap or reasoning gap?

Before you spend a week on a topic, it is worth establishing that the topic is the problem.

A concept gap looks like this: you cannot begin, or you begin with the wrong tool, and the explanation teaches you something you did not know. A reasoning gap looks different: the explanation teaches you nothing new, and your reaction is "I knew that" — which is usually true and is exactly why it keeps happening.

The second one is not fixed by re-reading the concept. Why you understand the concept and still get it wrong covers what to do instead.

All concepts

• Percentages

  The GMAT rarely tests whether you remember:

  Quantitative · Data Insights

• Data Sufficiency

  Data Sufficiency asks whether the supplied information determines one answer to the question. It does not ask you to calculate every available value.

  Quantitative

• Assumptions

  An assumption is an unstated claim the argument requires for its evidence to support its conclusion.

  Verbal

• Causal Reasoning

  A causal argument says that changing or observing X explains a change in Y. The GMAT tests whether the evidence isolates that relationship from…

  Verbal · Data Insights

• Graphics Interpretation

  GMAT Graphics Interpretation questions test whether you can decode what a visual represents before you calculate or infer from it.

  Data Insights