Pascal's Triangle and nCr

Counting & Binomials (Lesson 1/4)

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This lesson introduces powerful tools for counting the number of combinations in scenarios with many different possibilities.

In a combination, we are choosing some number of items from an existing set of items, and counting how many "subsets" we can make. For example, imagine the set {A,B,C,D}. How many subsets of 1 letter can I make?

{A},{B},{C},{D}makes 4 subsets

How about subsets with 2 letters?

{A,B},{A,C},{A,D},{B,C},{B,D},{C,D}makes 6 subsets