I don't know. But I guess it's kinda helpful knowing what the probability is.

10 questions, 3 (questions correct answered) correct answers

=>

5 choices per question;

probability for guessing the right answer is therefor

probability for guessing the wrong answer is therefor

=> probability("three right answers") =

the probability of guessing exactly 3 correct answers out of 10 is 20% (=0.2)