Suppose a math class has 24 students.

Question

In how many ways can four students be selected to take part in a survey?

In how many ways can four students be selected to do 4 different mathematical problems on the board?

Answer 1

²⁴C₄ = _{24!/4!(24-4)!}

   

       = 24!/4!*20!

 

        =462

 

So 462 ways