List the total number of possible outcomes. For example, if you have a bag containing three red marbles, four blue ones, five green ones and six black ones, add the marbles to get the total. Probability in this case involves pulling a ball without any bias; that means the marble is pulled out blindly. In this example, the addition yields 18.
Jot down the likelihood of a single possibility taking place. For example, determine that since there are four blue marbles, there are four chances of you drawing a blue marble from the bag. Similarly, for the black marbles, they number six within the bag.
Divide the chance of drawing one marble from the bag bearing the marbles. For instance, the chance or probability of drawing a green marble is 5/18. In the same way, probability of drawing a red marble is 3/18, drawing a blue one is 4/18 and drawing a black one is 6/18. Reduce the probabilities to the simplest form where possible. For example, 4/18 simplifies to "two to nine" and 6/18 simplifies to "one to three."