The Meeting Problem

Arrival times as a square

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

• Two random times form a random point in a square.
• Waiting $w$ minutes in an hour: $P(\text{meet}) = 1 - \left(1 - \frac{w}{60}\right)^2$.
• Probability becomes the area of a region in the square.

Steps

1. Two friends, one hour
2. Even odds
3. A quarter of an hour
4. Unequal patience
5. Ten minutes’ patience
6. Overlapping visits