Bertrand’s Paradox

What does "random" mean?

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Bertrand’s random chord problem has answers 1/3, 1/2 and 1/4 depending on the method.
• “Random” needs a specified probability distribution.
• Geometric probabilities are ratios of lengths, areas or angles.

Steps

1. A random chord
2. Check method 1
3. Check method 3
4. Which is right?
5. Three ways to pick a chord
6. Longer than the radius