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 not black?

Answer 1

Given: A bag contains 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. Number of balls that are not black

= Total – Black

= 20 – 7

= 13

3. Probability (not black)

= `"Number not black"/"Total"` 

= `13/20`

4. Alternatively,

P(not black) = 1 – P(black)

= `1 - 7/20`

= `13/20`

The probability that the ball drawn is not black = `13/20` = 0.65 = 65%.