Mr. Hauseman has 17 students in his class, three of whom are freshmen, and the rest are from other classes. He is going to draw two students randomly to be partners.

He calculates the probability of drawing a freshman and then a junior to be

9/136. How many juniors must be in the class?

a. 3 b. 6 c. 7 d. 8

Question

Mathematics

Justice

17 November, 11:41

Mr. Hauseman has 17 students in his class, three of whom are freshmen, and the rest are from other classes. He is going to draw two students randomly to be partners.

He calculates the probability of drawing a freshman and then a junior to be

9/136. How many juniors must be in the class?

a. 3 b. 6 c. 7 d. 8

+3

Answers (1)

Know the Answer?

Kaitlynn Ward · Answer 1

Let the number of sophomore be x, then

picking of one fresher is 3C1 and picking of one sophomore is xC1.

now probability = (3C1) (xC1) / [ (17C1) (16C1) ]

=3*x / (17*16)

since the probability = 3/34

so 3*x / (17*16) = 3/34

=>x=8

so the no. of sophomore is 8

option C is correct