The Same Size

Pairing up infinite sets

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 sets have the same size if they can be paired up one-to-one.
• Evens, integers, fractions and pairs of numbers are all countable: the same size as 1, 2, 3, …
• An infinite set can be the same size as part of itself.

Steps

1. Chairs and people
2. One-to-one correspondence
3. Integers too
4. Even the fractions
5. Where is 3/4?
6. Pairs of numbers