GO IN DEPTH

# Marble Mania

#### Materials

• A Marble Mania activity sheet for each student
• A few coins
• A blackboard or white board or big piece of paper and a marker
• Pencils or pens
• Computers with Internet access

Introduce your kids to probability and chance with a fun interactive. By flipping coins and pulling marbles out of a virtual bag, students begin to develop a basic understanding of probabilities, how they are determined, and how the outcome of an experiment can be affected by the number of times it is conducted.

### Background

Probability is the measure of how likely an event is. Flip a coin and what are your chances of getting heads? It's a 50-50 chance every time since there are two possible outcomes—heads or tails—that are equally probable. Of course, actual outcomes aren't necessarily the same as the probability for those outcomes. One coin flip and you get heads or tails, not half heads and half tails. Ten flips could give you seven heads even though chances are 50-50. But, the more tosses you do, the closer you can expect to come to a 50-50 outcome. Still, you don’t know what you’ll get each time.

### Activity Instructions

Set-Up

Do a little coin tossing to warm up for this activity. Ask kids what they think the chances are for a heads or a tails. Explain that there’s a 50-50, or 50 percent, chance or probability that the outcome will be "heads" or "tails." Point out that 50-50 is also a one in two chance or a ½ chance. Tell them that you’ll do this 10 times and ask them to predict what the outcome will be. Jot down the results on the board and discuss it.

Provide kids with the Marble Mania Record Sheet. Have kids pair off for a few minutes to do some coin tossing. They can record their guesses and the actual results of the coin tosses on the record sheet. Ask them: “If you could do 1,000 coin tosses, what do you predict would happen?” They may or may not know that the results would get closer to 50-50, but the point is that each time a coin is tossed, there’s no telling what the outcome will be.

Activity

Now lead your group in a demonstration of an online probability activity. Gather around a computer and pull up the Marble Mania interactive activity.

To mimic the coin toss, pick one red marble and one blue marble and plug in one pick and 10 trials. Ask kids what they think the outcome will be. Guide them to make the connection that there is a 50-50, or 50 percent, chance a red marble will be picked each time, just like the coin toss.

Once the results come up, discuss how the outcome is different from the chance or probability. Ask, “Do you think you could ever get a 50-50 outcome?”

Running a larger trial will pull up results closer to 50-50, but you still never know what the outcome will be each time. Run 50 or 100 trials and discuss the results.

Pick three marbles, one red and two blue. Plug in one pick and 10 trials. Ask kids what the chances are for red to be picked. Now, it’s a one in three chance for red to be picked.

Give each child a Marble Mania activity sheet and a pencil and point them toward the the student web page. The activity sheet will provide kids with the URL to access the interactive.

First, for simplification and better understanding, have kids use the tool to repeat the lesson's first marble experiment scenario that was conducted with only two marbles in the box. (This can be done by putting "1"s in the red and blue boxes, and "0"s in the yellow and green boxes.) To make the experiment similar to the original, kids also should select "1" marble to draw (per trial). Also make sure kids click on the "Clear Trial" button after running each trial. Kids can record their results on the activity sheet.

### Related Activities

Ever play heads or tails with your friends? It's fun when you're right. But each time you guess, there's no telling what will happen. Even if you just flipped ten heads in a row, there's still a 50-50 chance it'll be heads (or tails) again.