Combinations
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
A combination counts unordered selections: choosing r objects from n distinct ones gives C(n, r) = n!/(r!(n − r)!) ways.
Show
C(5, 2) = 10 — the 20 ordered pairs of Video 515, with each two-way swap counted once instead of twice.
Builds on
- Nothing — this is a starting point.
Unlocks
- Nothing yet depends on this.