Question

g In a multiple choice exam, there are 5 questions and 4 choices for each question (a, b, c, d). Nancy has not studied for the exam at all and decides to randomly guess the answers. What is the probability that: (a) the first question she gets right is the 5th question

Answer 1

81 / 1024

Explanation:

First, let's find the total number of ways that Nancy can choose random choices for the questions. This would be 4 * 4 * 4 * 4 * 4 = 4⁵ = 1024 because there are 4 choices and 5 questions. In order for first question she gets right to be the 5th question, she has to get the first 4 questions wrong. Therefore, since there are 4 choices for each question and only 1 of them is right, she has 4 - 1 = 3 options for the first 4 questions and only 1 option for the 5th one, so the total number of "successful" ways Nancy can do this would be 3 * 3 * 3 * 3 * 1 = 81. Therefore, the probability is 81 / 1024.