Suppose 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 the question. However, if she does not know the answer to a question, she still has a 20% chance of getting the right answer by guessing.
(a). If we choose a question at random from the exam, what is the probability that she will get it right?
* Can you explain this using a probability tree ?
[Math] How to use a probability tree
probability
Best Answer
So there is a $60\%$ chance the student answer it right and $40\%$ chance the student answers it wrong. I can't show how a probability tree works with only one question, so I'll show it for two.