Homework Sourse3 students are selected from a class that has 10 boys and 5
3 students are selected from a class that has 10 boys and 5 girls. What is the probability that 1 boy and 2 girls are selected?
Solution
The class has 10 boys and 5 girls. In all there are 15 students.
The number of ways in which 3 students can be selected is 3C15
=> 15! / 3!*12!
=> 455
The number of ways that those selected are 1 boy and 2 girls is 2C5*1C10
=> 5!/2!*3! * 10!/1!*9!
=> 100
The probability is the ratio of the desired events to the total number of events possible.
This is 100/455
The probability that of the 3 students selected 1 is a boy and 2 are girls is 100/455
