How to Teach Probability in Fifth Grade Math

An ordinary penny can be used to teach probability.

Understanding probability will not allow you to predict the future, but it will help you make an educated guess. When you know the probability of something occurring, then you know the likelihood of it coming to pass. As an example, almost everyone knows that a coin has a 50 percent chance of landing on heads and a 50 percent chance of landing on tails. Therefore, you can surmise that on average half of all coin tosses will be heads and half will be tails. You can illustrate this concept to your fifth grade class with a simple experiment.

Instructions

1. Ask your class if they know the probability of a coin toss coming up heads. They may say "half the time," which is correct. Explain that the coin has two sides, so the probability of either one of those sides coming up is one out of two. This is more precisely stated as a probability of 0.5, or 50 percent.

2. Draw two columns on the chalk board: one for heads and one for tails.

3. Have the first two student in the class flip a penny 10 times. For each toss, mark a line on either heads or tails, respective of the result.

4. Tally the results by adding the lines under each column and adding those two number together to record the total number of flips. As an example, if you recorded seven heads tosses and 13 tosses tosses, then the total number of tosses would be 20.

5. Divide each respective column's number by the total number of tosses to calculate the actual probability. In the example, you would find the calculated probability of the penny landing on heads was 0.35, or 35 percent. Tails would have a probability of 0.65, or 65 percent.

6. Ask the students why the numbers weren't exactly 50 percent. Explain that probability works on large numbers, and that over time, the more tosses you performed, the closer the probabilities would be to 50 percent. As an extreme example, you could ask about a single toss. With only one result, the calculated probabilities would be 0 percent and 100 percent, which is obviously misleading.

7. Continue the experiment with the rest of the class tossing the penny 10 times and tallying the results. You might end up with 146 heads tosses and 154 tails tosses. These numbers would correspond to 0.487, or 48.7 percent, for heads and 0.513, or 51.3 percent, for tails

References

• Education: Coin Toss Probability
• Dartmouth College: Introduction to Probability