There is a class with 15 boys and 30 girls, which equals a total of 45 students.

There is a class with 15 boys and 30 girls, which equals a total of 45 students.  If 10 students are selected at random for a special assignment, there is an equation to find the probability that exactly 3 boys will be selected.  Since the problem used is a combination of various factors (taking into account both boys and girls), the combination rule equation must be used.