Khan Academy (English - US curriculum)
Math by grade
Eureka Math/EngageNY
Precalculus (Eureka Math/EngageNY)
Module 5: Probability and statistics
Topic A: Lesson 2: Counting rules—The fundamental counting principle and permutations
Ways to pick officers
Ways to pick officers
How many ways can we pick officers for our organization?
License: CC BY-NC-SA by Khan Academy