A professor must randomly select 4 students to participate in a mock debate. There are 20 students in his class. In how many different ways can these students be selected, if the order of selection does not matter?

The equation we used in this problem is the combination of probability. The formula used is "nCr = n! / r! * (n - r) !" where, n is all 20 students and r is the 4 students. Substituting the numbers we get 4845 ways.