Question

There are 20 students in a math class. Thirty percent of the

students are randomly chosen to participate in a teacher
evaluation. How many combinations of students are possible?

Answer 1

Explanation:

20% of 30 is 6 are randomly selected.

30 choose 6 = 30! / (30-6)! 6!

= 30! / 24!6!

= 30 * 29 * 28 * 27 * 26 * 25

--------------------------------- <-- 24! cancels

6 * 5 * 4 * 3 * 2 * 1

= 29 * 28 * 27 * 26 * 25

---------------------------------- <--- 30 = 6 * 5 cancels

4 * 3 * 2 * 1

= 29 * 7 * 9 * 13 * 25 <-- 4 cancels 28, 3 cancels 27, 2 cancels 26

= 593775