Counting Methods (VCE SSCE Mathematical Methods): Flashcards

Choosing between alternatives (or)

Sequential choices (and)

Arrangements where order matters

Selections where order doesn't matter

$\frac{n!}{(n-r)!}$

$\frac{n!}{r!(n-r)!}$

Multiply all whole numbers from that number down to 1

$120$

Order matters = permutations; order doesn't = combinations

$\binom{n}{r}$