This is an example of a binomial experiment or a Bernoulli trial.
p = 1/4. the probability of guessing a correct answer.
q = 1 - p = 3/4, the probability of guessing a wrong answer.
The probability of guessing 3 out of 5 questions is
[tex]_{5}C_{3} \,p^{3}q^{5-3} = \frac{5!}{3!2!}( \frac{1}{4})^{3}( \frac{3}{4})^{2} = 0.088[/tex]
Answer: 0.088
