The number of ways to choose k out of n things is ______.
A)the number of ways to choose k - 1 out of n - 1 things
B)the number of ways to choose k out of n - 1 things
C)the sum of the number of ways to choose k - 1 out of n - 1 things and the number of ways to choose k out of n - 1 things
D)the product of the number of ways to choose k - 1 out of n - 1 things and the number of ways to choose k out of n - 1 things

Question

Quizplus · Accepted Answer

This is a principle of combinatorics that states the number of ways to choose $k$ items from $n$ items is equal to the sum of the number of ways to choose $k-1$ items from $n-1$ items (choosing a specific item) and the number of ways to choose $k$ items from $n-1$ items (not choosing that specific item). This principle is known as Pascal's rule.

The Number of Ways to Choose K Out of N