Question

The probability of guessing a correct answer x/2 and not guessing an answer is 2/3 .Then find x

Answer 1

Let E denote the event of guessing a correct question and E bar denote the event of not guessing a correct question .

Given probability of guessing a certain question is P(E) = (x/2)

Hence probability of not guessing answer isP(E') = (2/3)

P(E) + P(E') = 1

x / 2 + 2 / 3 = 1

x / 2 = 1 / 3

∴x = 2/ 3.