Question

A bag contains 20 balls numbered from 1 to 20. One ball is drawn at random from the bag. What is the probability that the ball drawn is marked with a number which is multiple of 3 or 4?

Answer 1

Number of balls = 20
∴ n ( S ) = 20
Number of balls marked with multiple of 3 or 4 is 3, 6, 9, 12, 15, 18, 4, 8, 16, 20
∴ n (A) = 10

The required probability P (A) = `(n(A))/(n(s)) = (10)/(20) = (1)/(2)`.