Factorials & Ordered Arrangements

When distinct objects fill ordered positions, the number of available choices shrinks one position at a time, creating factorial products.

What you'll learn

  • Build an ordered-arrangement count by multiplying the shrinking number of choices for successive positions.
  • Interpret n! as n × (n−1) × ··· × 2 × 1 and explain 0! through the single empty arrangement.
  • Decide whether order and object distinctness make a factorial count valid without adjustment.

Before you start

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