Question

You have to answer 2 questions for the exam. There are 7 essays to choose from. How many different groups of 2 essays could you possibly choose?

Answer 1

21

Explanation:

Since the order of the essays isn't important, the number of ways you can choose 2 from 7 is:

₇C₂ = 7! / (2! (7−2)!)

₇C₂ = 7! / (2! 5!)

₇C₂ = 7×6×5! / (2×1 × 5!)

₇C₂ = 7×6 / 2

₇C₂ = 21