For problems 3-5, in a class of 40 students, 24 are over the age of 21 and 16 are 21 or younger. Biff is over the age of 21. A student is selected at random. (3 pts each) 3. Find the probability the student is over the age of 21.4. Find the probability Biff was selected if you know the student selected was over the age of 21. 5. Find the probability Biff was selected if you know the student selected was 21 or younger

3. 60% probability the student is over the age of 21.

4. 4.17% student is over the age of 21.4. Find the probability Biff was selected if you know the student selected was over the age of 21.

5. 0% probability Biff was selected if you know the student selected was 21 or younger

Step-by-step explanation:

A probability is the number of desired outcomes divided by the number of total outcomes.

In this question, we have that:

There are 40 students.

Of those, 24 are over the age of 21.

The other 16 are 21 or younger.

3. Find the probability the student is over the age of 21.

Of the 40 students, 24 are over the age of 21.

24/40 = 0.6

60% probability the student is over the age of 21.

4. Find the probability Biff was selected if you know the student selected was over the age of 21.

There are 24 students over the age of 21, and Biff is one of them.

1/24 = 0.0417

4.17% student is over the age of 21.4. Find the probability Biff was selected if you know the student selected was over the age of 21.

5. Find the probability Biff was selected if you know the student selected was 21 or younger

Biff is older than 21, so if the student selected is 21 or younger, it cannot have been Biff.

So

0% probability Biff was selected if you know the student selected was 21 or younger