Question: There are 50 balls, each ball having two colours, one black or white and the other red, orange or green as shown in the following table:
| Red | Orange | Green | Total | |
| Black | 3 | 12 | 15 | 30 |
| White | 7 | 3 | 10 | 20 |
| Total | 10 | 15 | 25 | 50 |
(It means there are three balls, which are black and red, 12 balls are black and orange and so on.)
If of these balls, one ball is selected at random, find the probability of each type of ball being drawn up.
Solution:
Probability Table
| Red | Orange | Green | Total | |
| Black | 0.06 | .24 | .30 | 0.60 |
| White | 0.14 | .06 | .20 | 0.40 |
| Total | 0.20 | .30 | .50 | 1.00 |