Question

Twelve students ask to visit a college admissions counselor. The counselor can meet with one student at a time. in how many ways can seven time slots be assigned?

I know how to do this, I just don't know whether or not to use nCr or nPr.

Answer 1

You use combinations if order doesn't matter, and permutations if order does matter. Does the order the students are seen matter in this problem?

Answer 2

Doesn't seem like it. so the answer is 792?

Answer 3

I think order *does* matter. It's a completely different situation if Alice is seen at 9:00 and Bob is seen at 10:00 than the other way around, right? So I'd say use permutations.

If the problem were "How many ways can the counselor choose seven people to see?" then combinations would be used, but the students are *not* just being chosen, they're filling up specific spots.

Answer 4

ohhh. Alright. Thank you. I always have a hard time with those kinds of problems. It's a shame, because the process is so easy once you know which method to go with. :/

Answer 5

It's good you have the factorial stuff down! Just think "After I choose them, does it matter where I put them?" If the answer is yes, then use permutations (which will ALWAYS be a higher number than combinations).

Answer 6

choose = C = combinations.
put = P = permutations.

For what it's worth.

Answer 7

Thanks!