Question

Last year at a certain high school, 12 students sought the nomination for president of the student body. In how many ways could the voters (student body) rank their first 4 choices?

Answer 1

495 different ways

Explanation:

This question bothers on combination. Combination has to do with selection. When selecting r objects from a pool of n objects, this is expressed as;

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

For us to choose rank the first 4 choices from 12 students nominated, this can be done in 12C4 number of ways;

12C4 = 12!/(12-4)!4!

12C4 = 12!/8!4!

12C4 = 12*11*10*9*8!/8!*4*3*2

12C4 = 12*11*10*9/24

12C4 = 11880/24

12C4 = 495 ways

Hence this can be done in 495 different ways