Suppose we have a box which contains four balls, colored red, blue, green, and yellow.
If we draw two balls at random from the box, what is the chance that one is yellow and the other red?
The first thing to do is to make a list of the possible outcomes of a draw:
We see that only one of the outcomes contains a yellow and a red ball out of a total of 6 possibilities. Therefore, the chance of drawing a pair containing a yellow and a red ball is 1 in 6.
So we say, the probability of drawing a pair containing a yellow and a red ball is 1/6.
