Question

A recent survey shows that the probability of a college student drinking alcohol is 0.6. Further, given that the student is over 21 years old, the probability of drinking alcohol is 0.8. It is also known that 30% of the college students are over 21 years old. Of the students who are not over 21, what is the probability they drink alcohol? Group of answer choices

Answer 1

Answer: 0.5143

Explanation:

Probability of students who are over 21 years old = 30% = 0.3

Probability of students who are under 21 years old = 100% - 30% = 70% = 0.7

Probability of drinking alcohol for over 21 = 80% = 0.8

Probability of not drinking alcohol for over 21 = 100%- 80% = 20% = 0.2

Let the probability of the students who are not over 21, that drink alcohol be p.

Total probability of a college student drinking alcohol = (0.3 × 0.8) + (0.7 × p)

0.6 = (0.3 × 0.8) + (0.7 × p)

0.6 = 0.24 + 0.7p

0.7p = 0.6 - 0.24

0.7p = 0.36

p = 0.36/0.7

p = 0.5143

The probability of the students who are not over 21, that drink alcohol is 0.5143.