Remove the pennies that land tail side up and put them flat on the left side of the table, arranged in a tall column.Gather up the remaining pennies and toss them again.Rarely will exactly 1/2 of the coins or 1/6 of the cubes decay on the first toss.
If no pennies come up tails on a toss, leave an empty column.
You can do the same thing with the wooden cubes, if you have them, removing the cubes that land red side up.
This type of pattern—in which a quantity repeatedly decreases by a fixed fraction (in this case, 1/2)—is known as exponential decay (click to enlarge photo below).
Each time you toss the remaining pennies, about half of them are removed.
The second lesson, Radioactive Decay: a Sweet Simulation of Half-life, introduces the idea of half-life.