Question

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

Answer 1

3. 60% probability the student is over the age of 21.4

4. 4.17% 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

Explanation:

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

In this question:

40 students

24 over the age of 21.

16 are 21 or younger.

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

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

24/40 = 0.6

60% probability the student is over the age of 21.4

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

24 students over the age of 21, one of which is Biff.

1/24 = 0.0417

4.17% 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 not 21 or younger, he is over 21, so there are no desired outcomes.

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