Suppose that you take a 20 question multiple-choice quiz by guessing. Each question has exactly one correct answer of the four alternatives given. What is the probability of getting all 20 questions correctly?
1 Answer
We can therefore say, very roughly, that the probability is slightly over one trillionth.
Explanation:
For each question, there is a probability of
One the first question, therefore, we have the probability of
We can generalize and say that for any number of questions where we are guessing among 4 answers each time, the probability of getting them all right is:
For 20 questions, we have:
We can therefore say, very roughly, that the probability is slightly over one trillionth.