Answer: 53,130 possible combinations
Step-by-step explanation:
First, we want to find how much is the 20% of 25.
This is:
N = (20%/100%)*25 = 5.
So 5 students out of 25 are selected.
When we want to calculate the number of combinations of N elements it a group of K elements, we have:
[tex]C = \frac{N!}{(N - K)!*K!}[/tex]
Here N = 25, and K = 5
[tex]C = \frac{25!}{20!*5!} = \frac{25*24*23*22*21}{5*4*3*2*1} = 53,130[/tex]
so we have 53,130 combinations.