Question

Suppose that a student who is about to take a multiple choice test has only learned 40% of the material covered by the exam. Thus, there is a 40% chance that she will know the answer to a question. However, even if she does not know the answer to a question, she still has a 20% chance of getting the right answer by guessing. If we choose a question at random from the exam, what is the probability that she will get it right?

Answer 1

Answer:

There is a 52% probability that she will get it right.

Step-by-step explanation:

We have these following probabilities:

A 40% probability that the student knows the answer to a question.

A 60% probability that the student does not know the answer to a question.

If the student does not know the answer to a question, a 20% probability of getting the question right guessing.

If we choose a question at random from the exam, what is the probability that she will get it right?

40% probability that she knows the answer

60% that she has to guess, when there is a 20% probability of getting it right. So

$P = 0.4 + 0.6*0.2 = 0.52$

There is a 52% probability that she will get it right.