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Message: <blockquote data-quote="Joseph" data-source="post: 1974147" data-attributes="member: 214925">First of all, you need to find out how many different arrangements or combinations of 4 correct answers exist. This is 5 C 4 = 5.So the student can answer 4 correct questions in 5 different ways (each way corresponding to one of the 5 questions being answered wrong).The student's chance of guessing the correct answer for any question is 25%  (1 out of 4). The student's chance of guessing 4 correct answers is (0.25)^4 = 3.9 * 10 ^-3Since these can occur in 5 different combinations, the required probability is 5* 3.9 * 10^-3 = 0.02 (roughly).Hope that helped.</blockquote>