Ask your students to define probability. You may need to guide them, but once your class has collaboratively arrived at the correct definition, write it on the board for them to refer to if necessary.
Give your students a practical example of probability in action. Take a coin, and ask your students roughly how long it would take to flip heads 10 times in a row. The probability of this happening is 1/1024. Therefore, it would take someone flipping the coin quickly several hours to achieve the feat. Now take a dice and ask your students to guess how long it would take them to roll a six 10 times in a row. The answer may be surprising. The odds of a person rolling a six 10 times in a row is 1/60466148. Assuming one roll every 10 seconds, it would take a person almost 20 years to roll a six 10 times in a row. Explain that the difference between the two is that in the case of the dice there are many more potential outcomes. Probability theory is a way of using the number of potential outcomes to discover how likely any one outcome, or combination of outcomes, is in reality.
Explain to your students that probability can be expressed as a percentage, a fraction or a ratio. Give the students some simple probability questions, and ask them to display the answer as a percentage, then a fraction, then a ratio. For example, you could ask them: "There are 10 rows of seats in a cinema. What is the probability that Johnny will sit in the fourth row?" The answer would be 10 percent, 1/10th and 1:10
Give your students some more challenging probability questions to test their understanding of the topic thus far. For example, hand out a plan of your classroom with the seats arranged in colored sections of different sizes. Ask your students to give the probability that a person would sit in each section.
One crucial aspect of any teacher's job is relating the material to the student's lives so that they feel as though they've learned something worthwhile. This is especially true of mathematical subjects, which can seem a little abstract. Ask your students to name jobs which involve probability. Examples include doctors and psychologists, who sometimes need to use probability to determine the most viable course of treatment for their patients, actuaries and mathematicians.