Question

HELP PLEASE! Fred enrolled in college to pursue a degree in physics. He is told there is a 70% chance that he will get less than 60 on his first test. He is also told if he gets less than 60 on this test, the probability he passes the course is 55%. Otherwise, there is a 70% chance he passes the course. What is the probability he gets more than 60 on the first test, but fails the course? A. 0.12 B. 0.09 C. 0.21 D. 0.30​

Answer 1

Explanation:

Fred has two possible outcomes on his first test: he either scores less than 60 or he scores 60 or higher.

If he scores less than 60, there is a 55% chance he will pass the course, and a 45% chance he will fail. We know there is a 70% chance he will score less than 60, so the probability that he scores less than 60 and fails the course is 0.7 * 0.45 = 0.315.

If he scores 60 or higher, there is a 70% chance he will pass the course, and a 30% chance he will fail. We don't know the exact probability that he scores 60 or higher, but we know that it is 1 - 0.7 = 0.3 (since there is a 70% chance he scores less than 60). So the probability that he scores 60 or higher and fails the course is 0.3 * 0.3 = 0.09.

Adding these two probabilities together gives us the total probability that Fred gets more than 60 on the first test but fails the course: 0.315 + 0.09 = 0.405. However, we are looking for the probability that he gets more than 60 but fails, so we need to subtract the probability that he scores less than 60 and fails: 0.405 - 0.315 = 0.09. Therefore, the answer is B. 0.09.

i think so...