Question

In an examination, 20 questions of true – false type are asked. Suppose a student tosses fair coin to determine his answer to each question. If the coin falls heads, he answers ‘true,’ if it falls tails, he answers “ false’. Find the probability that he answers at least 12 questions correctly. Select the correct answer from above options

Answer 1

Probability that student answers a question true = 1 2 i.e., when a coin is thrown, probability that a head is obtained = 1 2 Probability that his answer is false = 1 - 1 2 = 1 2 Probability that his answer at least 12 questions correctly = P (12) + P (13) + P (14) +…….. P (20)