A bag contains 5 red, 8 white and 7 black balls. A ball is drawn at random from the bag. Find the probability that the drawn ball is

Total no. of possible outcomes = 20 {5 red, 8 white & 7 black}

(i) E ⟶ event of drawing red or white ball

No. of favourable outcomes = 13 {5 red, 8 white}

Probability, P(E) = (No.of favorable outcomes)/(Total no.of possible outcomes)

P(E) = 13/20

(ii) Let E ⟶ be event of getting black ball

No. of favourable outcomes = 13 {5 red, 8 white}

P(E) = 7/20

(Bar E)⟶ event of not getting black ball

P(Bar E) = 1 – P(E)

=1−7/20 = 13/20

(iii) Let E ⟶ be event of getting neither white nor black ball

No. of favourable outcomes = 20 – 8 – 7 = 5 {total balls – no. of white balls – no. of black balls}

P(E) = 5/20 = 1/4