Probability Problem, permutation or combination

There are 326 students in the class. If each student shakes hands with every student, how many handshakes will take place?
If each student gives every student a Halloween treat, how many treats will be exchanged?

I'm not sure whether to use the equations for permutation or combination. Also, wouldn't the answer for both be the same :s

You might want to look at the first question this way: assign a number to each student, from 1 to 326. So one handshake would be, for example, student 3 with student 85. We can write that as (3,85). However, when student 85 shakes hands with student 3, that doesn't count as a separate handshake. In other words, the order does NOT matter, so it's a case of combination. Also, in order to specify the right formula, you have to see if there is repetition or not. Can student 54 shake hands with student 54? No, it makes no sense, so there is no repetition. To illustrate the problem better, it is always good to find some solutions or "groups" and write them down. I already made this easier by assigning a number to each student, from 1 to 326. Here are some of the possibilities of handshakes:

{(1,2), (1,3), (2,5), (17,257), (112, 88) etc...}

Again, remember that the list of groups cannot include, for example, both (2,5) AND (5,2) because the order does not matter (it's the same two people, so there's only one handshake between them). Also, for example, the group (7, 7) cannot exist because student 7 cannot shake hands with himself or herself.

So we've defined that in the groups that we are looking for, the order does not matter, which means it's a combination problem, and there is no repetition. Therefore, the formula which will give us the total number of handshakes between the 326 students is:

C = m! / [n!(m - n)!]

m = the total number of elements, which is 326 students
n = the total number of elements per group, which is 2 (see the examples above).