Question

A bag contains 4 white balls, 6 red balls, 7 black balls and 3 blue balls. One ball is drawn at random from the bag. What is the probability that the ball drawn is neither white nor black?

Answer 1

Given: A bag with 4 white, 6 red, 7 black and 3 blue balls; one ball is drawn at random.

Step-wise calculation:

1. Total number of balls

= 4 + 6 + 7 + 3

= 20

2. Favourable outcomes (neither white nor black)

= Red + Blue 

= 6 + 3

= 9

3. Probability = `"Favourable"/"Total"`

= `9/20`

Alternatively: P = 1 – P(white or black)

= `1 - (4 + 7)/20`

= `1 - 11/20`

= `9/20`

The probability that the ball drawn is neither white nor black is `9/20` = 0.45 = 45%.