Absolute Dating Practice Problems

Now that you understand how absolute dating works, you will practice applying your knowledge by completing the following activities.

Before practicing your skills, here is an example to help prepare:

Example Activity

Imagine you have a jar filled with 100 glowing marbles. These marbles don’t glow forever—each one will eventually stop glowing. But here’s the special part:

• The marbles fade in a predictable way.
• Every hour, half of the glowing marbles stop glowing.
• That “hour” is the half‑life.

At the start (0 hours) all 100 marbles are glowing.

After 1 half-life (1 hour): Half of the marbles stop glowing.
✨ 50 marbles are still glowing.

After 2 half-lives (2 hours): Half of the remaining 50 marbles fade.
✨ 25 marbles still glowing.

After 3 half-lives (3 hours): Half of the 25 remaining marbles fade.
✨ 12.5 marbles still glowing.

Each point on the graph represents a stage where half of the remaining marbles stop glowing. It starts with 16 glowing marbles and goes down to just 1 after four half-lives.

Now it is your turn to use your knowledge of half-lives and radioactive isotopes to complete the following

You can click on the arrows at the bottom right to enlarge the slide.