The total number of students is composite provided that there's at least 2 students per group.
This deals with the definition of a prime number and a composite number.
prime number - This is a number that can only be evenly divided by itself and 1. No other number can evenly divide a prime number. Some examples would be 2, 3, 5, 7, 11, 13 ....
composite number - This is a number that's the product of 2 or more prime numbers. Because of that, a composite number can be evenly divided by more than just itself and one.
Since each of the 3 groups of students has the same number of students, that means that the total number of students is evenly divisible by 3. Assuming that there's at least 2 students per group, that would mean that the total number of students is a composite number.
If there's exactly 1 student per group, then the total number of students is prime. But since group implies more than 1, this is unlikely.
