math
posted by jane .
Decide if it's permuatation or combination .
1how many teams of 4 horses be made if there were 9 horses in total ?
2mike has nice baseball trophies to arrange on the shelf . How many different ways can be arranged ?
3in a math class , there are 24 students,the teacher picks 4 students to help do a demonstration.how many diffrent groups of 4 could she have chosen ?

1. We can't tell from the question. If the position of a particular horse in the team is important, then it is a permutation. If you just care about groups of 4 horses, then you have a combination. I think the placement of a horse should be important
2. combination
3. combination, unless members of the group have specific tasks in the demonstration.
1. Permutation: 9x8x7x6 = P(9,4) = 3024
combination : C(9,4) = 126
2. 9!
3. C(24,4) = 10626