Question

Alex takes a multiple-choice quiz in his Anthropology 100 class. The quiz has 10 questions, each has 4 possible answers, only one of which is correct. Alex did not study for the quiz, so he guesses independently on every question. What is the probability that Alex answers exactly 2 questions correctly

Answer 1

Answer:

The probability is 0.28157

Step-by-step explanation:

The number of answers are 40 answers ( 10 questions and 4 answer each)

The number of correct answers is only 10

So the probability that he answers 2 exactly out of 10 means he correctly selected 2 answers

The probability will be;

10 C 2/ 40 C 10

This mean out of the total 10 correct, he selects 2 and out of the total 40 , he selects 10

The probability of selecting a correct answer is;

1/4 while the probability of selecting a wrong one is 3/4

So probability of selecting 2 correct out of a total 10 will be

10 C 2 (1/4)^2 (3/4)^8

= 0.28157