Question

A box containing 3 red, 3 white and 3 green balls. A ball is selected at random. Find the probability that,

(iii) ball picked up is neither white nor red.

Answer 1

One ball is drawn at random from a bag containing 3 red balls (R1, R2 and R3), 3 white balls (W1, W2 and W3) and 3 green balls (G1, G2 and G3).
∴ S = {R1, R2, R3, W1, W2, W3, G1, G2, G3}
Or,
n(S) = 9
Now,
C is the event that the ball picked is neither white nor red.
∴ C = {G1, G2, G3}
Or,
n(C) = 3
Thus, we have:
P(C) = $\frac{n\left(C\right)}{n\left(\mathrm{S}\right)}=\frac{3}{9}=\frac{1}{3}$