In a box, there are 9 red, 7 blue and 5 green balls. One ball is picked up randomly. What is the probability that it is neither red nor green?
1/3
Total number of balls = (9 + 7 + 5) = 21.
Let E = event that the ball drawn is neither red nor green.
= event that the ball drawn is blue.
∴ n(E) = 7.
∴ P(E)= 13.