The Multiplication Principle

Choices multiply

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Independent choices multiply.
• $k$ positions with $n$ options each give $n^k$ possibilities.
• Small increases per position compound enormously.

Steps

1. Outfits
2. The multiplication principle
3. Licence plates
4. Or, not and
5. Optional dessert
6. A trillion passwords
7. Password strength