On a multiple cho

This question is based on Bernoulli’s distribution.

Here the experiment is to get 4 or more correct answers by guessing n=5 questions.

There are three possible answers, P(getting correct answer)

⇒

And P(getting wrong answer)

⇒

Let X be the number of correct answers, then

⇒ where x=0,1,….,n. and p+q=1

Now we have to calculate

P(getting 4 or more correct answers)=P(4)+P(5)

⇒

⇒

⇒