College Algebra / Unit 9 Alg 513 short lesson, about 20 seconds
Factorials
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The idea
The factorial n! multiplies the counting numbers from n down to 1, counting the orderings of n distinct objects; by convention, 0! = 1.
In practice
4! = 4 · 3 · 2 · 1 = 24 — four choices for first place, three for second, the Multiplication Principle run to the floor.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
- Nothing. This is a starting point.
Unlocks
- Nothing yet depends on this.
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