Question

A bag contains 5 black, 7 red and 3 white balls. A ball is drawn from the bag at random. Find the probability that the ball drawn is:

(i) red (ii) black or white (iii) not black

Answer 1

Given: A bag contains 7 red, 5 black and 3 white balls and a ball is drawn at random

Required to find: Probability of getting a

(i) Red ball

(ii) Black or white ball

(iii) Not black ball

Total number of balls 7 + 5 + 3 = 15

(i) Total number red balls is 7

We know that, Probability = Number of favourable outcomes/ Total number of outcomes

Thus, the probability of drawing a red ball = 7/15

(ii) Total number of black or white balls is 5 + 3 = 8

We know that, Probability = Number of favourable outcomes/ Total number of outcomes

Thus, the probability of drawing white or black ball = 8/15

(iii) Total number of black balls is 5

We know that, Probability = Number of favourable outcomes/ Total number of outcomes

Thus, the probability of drawing black ball P(E) = 5/15 = 1/3

But, this is not what is required.

And, we know that sum of probability of occurrence of an event and probability of non-occurrence of an event is 1

Thus, the probability of drawing a card that is not black is 2/3.