Discrete Math

Question

A classroom has 12 students. The teacher would like to pick a group of 4 students to present on a

topic. How many different combinations of 4 students could the teacher choose from?

Answer 1

_nC_r = n! / (r!)(n - r)!

₁₂C₄= 12! / (4!)(12 - 4)!

₁₂C₄ = (12 · 11 · 10 · 9) / (4 · 3 · 2 · 1)

₁₂C₄ = 495

Answer 2

12/4 = 3 different groups