In a multiple choice question there are four alternative answers of which one or more are correct. A

Question

In a multiple choice question there are four alternative answers of which one or more are correct. A candidate will get marks in the question only if he ticks the correct answers. The candidate decide to tick the answers at random. If he is allowed upto three chances to answer the questions, find the % probability that he will get marks in the question.

Professor PC Thomas Classes · Answer

The total number of ways to answer the question\ ${ }^{4} C_{1}+{ }^{4} C_{2}+{ }^{4} C_{3}+{ }^{4} C_{4}=2^{4}-1=15$\ Required Probability $=$ Probability of correct answer in I chance + Probability of correct answer in II chance + Probability of correct answer in III chance\ $=\frac{1}{15}+\frac{14}{15} 	imes \frac{1}{14}+\frac{14}{15} 	imes \frac{13}{14} 	imes \frac{1}{13}=\frac{1}{5}$.