The product rule for counting (AQA GCSE Further Maths): Flashcards

Multiply the number of options at each step

$n \times (n-1) \times (n-2) \times ... \times 2 \times 1$

$1$

$4 \times 3 \times 2 \times 1 = 24$

$5,040$

$6! = 720$

Handle the most restrictive conditions first

$6 \times 5 \times 4 \times 3 = 360$

$5 \times 4 \times 1 = 20$ (last digit = 8)

Each choice is independent

When order matters

$408$