Question

A bag contains 3 red balls, 5 black balls and 4 white balls. A ball is drawn at random from the bag. What is the probability that the ball drawn is :

(i) white ? (ii) red ? (iii) black ? (iv) not red ?

Answer 1

Number of possible events = 3+5+4=12 balls

(i) Let A be the favourable event such that it is a white ball.

$\therefore P\left(A\right)=\frac{4}{12}=\frac{1}{3}$

(ii) Let B be the favourable event such that it is a red ball.

$\therefore P\left(B\right)=\frac{3}{12}=\frac{1}{4}$

(iii) Let C be the favourable event such that it is a black ball.

$\therefore P\left(C\right)=\frac{5}{12}$

(iv) Let D be the favourable event such that it is not red.

$\therefore$ Number of favourable events = 5 + 4 = 9

$\therefore P\left(D\right)=\frac{9}{12}=\frac{3}{4}$