JEE Main 2013 — Probability Question with Solution

Each question has 3 alternative and exactly one is correct.

$$\therefore$$ Probability of giving correct answer P(correct) = $$\frac{1}{3}$$

$$\therefore$$ Probability of giving wrong answer P(wrong) = $$\frac{2}{3}$$

Here student give 4 or more correct answer.

$$\therefore$$ Student give either 4 correct answer or 5 correct answer.

Using Binomial Distribution,

Required probability = $${}^5{C}_4{\left(\frac{1}{3}\right)}^4{\left(\frac{2}{3}\right)}^1$$ + $${}^5{C}_5{\left(\frac{1}{3}\right)}^5{\left(\frac{2}{3}\right)}^0$$ = $$\frac{11}{3^5}$$