Question

In a class of 7, there are 2 students who are martial arts masters.

If the teacher chooses 2 students, what is the probability that both of them
are martial arts masters?

Answer 1

1/21

Explanation:

First, find the possible number of combinations of 2 students picked from 7 since order does not matter:

7 choose 2 = 7 nCr 2 = 7!/2!(7-2)! = 5040/2(120) = 5040/240 = 21

Because there's only one combination where both students are martial arts masters, the probability of selecting 2 students out of 7 given that 2 of the 7 are martial art masters is 1/21.