Question

There are 10 students in a class: 3 boys and 7 girls. If the teacher picks a group of 3 at random, what is the probability that everyone in the group is a girl?

Answer 1

2/3 is the probability

Answer 2

Probability the first pick is a girl: 7/10

Probability the second pick is a girl: 6/9

Probability the third pick is a girl: 5/8

Probability of picking 3 girls: 

7/10 * 6/9 * 5/8 = 

= (7 * 6 * 5)/(10 * 9 * 8) 

= (7 * 1 * 1)/(2 * 3 * 4)

=7/24

Approximately 0.29 = 29%