Permutation And Combination Q42

42.How many combinations of students are possible if the group is to consist of exactly 3 freshmen?

	A.	5000
	B.	4550
	C.	4000
	D.	3550

Answer – (B)

Solution:

Here we need the number of possible combinations of 3 out of 5 freshmen,C35, and the number of possible combinations of 3 out of the 15 sophomores and juniors, C315.
Note that we want 3 freshmen and 3 students from the other classes.
Therefore, we multiply the number of possible groups of 3 of the 5 freshmen times the number of possible groups of 3 of the 15 students from the other classes.
C35*C315= 4,550