Activities
Make a Number Chart
Build a 1–100 chart and circle every multiple of 7 — patterns appear instantly.
A 1–100 chart is just ten rows of ten numbers. Plain at first — until you start colouring patterns in. Then it becomes a map of the number system.
Try these patterns
- Colour every multiple of 2 — you get stripes
- Colour every multiple of 5 — two clean columns
- Colour every multiple of 3 — diagonals appear
- Colour every prime — randomness with a hidden rule
Once you've coloured multiples of 2, 3 and 5, the survivors below 100 are nearly all primes. That's the Sieve of Eratosthenes — done by hand.