multiple choice question has 5 available options, only 1 of which is correct. Students are allowed 2 attempts at the answer. A student who does not know the answer decides to guess at random, as follows: On the first attempt, he guesses at random among the 5 options. If his guess is right, he stops. If his guess is wrong, then on the second attempt he guesses at random from among the 4 remaining options. Find the chance that the student gets the right answer at his first attempt.
the prob(correct guess on first try) = 1/5
Did you leave out a second question?
The interesting part of the problem does not get involved
e.g. What is the probability that he will guess correctly after either one or two tries.?
No, the interesting part is how come someone needs help on the simplest of questions? Obviously learnt nothing during the edX course, as s/he has to get someone else to answer the questions for them.
To find the chance that the student gets the right answer on his first attempt, we need to determine the probability of randomly selecting the correct option out of the total 5 options.
Since there is only 1 correct option out of 5, the probability of selecting the correct answer on the first attempt is 1/5 or 0.2 (20%).
Therefore, the chance that the student gets the right answer on his first attempt is 0.2 or 20%.