Product rule for counting

Definition

A counting rule which multiplies the number of choices at successive stages.

Used by AQA, Edexcel and OCR

Specification N5 · Paper 1, Paper 2, Paper 3

Specification N5 · Paper 1, Paper 2, Paper 3

A counting principle stating that if one task can be completed in $m$ ways and, for each of these, a second task can be completed in $n$ ways, the two tasks can be completed in ways.

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n

m \times n

Specification 11.02b · Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Foundation), Paper 4 (Higher), Paper 5 (Higher), Paper 6 (Higher)

A counting rule: when a process has successive stages with fixed numbers of choices, multiply the numbers of choices to find the total number of outcomes.
This is the product rule for counting.
Revise: Enumeration Strategies