Question

In how many ways can 4 students from a group of 9 be seated in a row of 4 chairs?

I tried 9C4 = 126, 126C4
am I going the right direction?

thanks in advance

Answer 1

You have chair nr. 1, chair nr.2, chair nr. 3 and chair number 4. If you seat a student at chair nr. 1 first, then at chair nr. 2, etc., then you have 9 choices for to choose the student who will sit in chair nr. 1, then 8 choices for who to seat in chair nr. 2 etc. etc., so the total number of posibilities is:

9*8*7*6

You can also say that there are
Binomial[9,4] ways to choose 4 students out of 9. And then there are 4! ways to choose a seating order for any given choice of the students:

Binomial[9,4] 4! = 9!/5! = 9*8*7*6

Answer 2

I understand now, thanks!