Discussion Forum

A multiple-choice examination has 5 questions, Each question has three alternative answers of which exactly one is correct. The probability that a student will get 4 or more correct answers just by guessing is 

Answer:

Explanation:

The probability of guessing a correct answer, p=1/3 and probability of guessing

wrong answer ,q$=\frac{2}{3}$

    $\therefore$ The probability of guessing a 4 or more correct answer

    = $^{5}C_{4}\left(\frac{1}{3}\right)^{4}.\frac{2}{3}+^{5}C_{5}\left(\frac{1}{3}\right)^{5}$

$=5.\frac{2}{3^{5}}+\frac{1}{3^{5}}=\frac{11}{3^{5}}$