Problema Solution
A class has 20 students. If the teacher is randomly putting students in groups of 3 to complete a project, what is the probability that three students who are best friends will be together?
1/20
3/20
1/1,140
Answer provided by our tutors
The total number of different groups of 3 is:
C(20, 3) = 20!/((20 - 3)!3!)
C(20, 3) = 18*19*20/6
C(20, 3) = 1140 groups
Since the 3 friends make only 1 group out of the total of 1140 groups the probability that the best friends will be together is:
p = 1/1140