Month: November 2025

We looked at a brilliant puzzle today:

Schur numbers tell you highest number that you can count to using k different colours before you’re forced to have an all same-coloured solution to a + b = c.

You’re trying to avoid this:

Two numbers of the same colour add up to another number of the same colour.

In other words:

If you have red 2 and red 3, then red 5 would break the rule (because 2 + 3 = 5, and they’re all red).

If you have blue 2, then blue 4 would break the rule (because 2 + 2 = 4 and they’re all blue).

So, you want to colour the numbers so this never happens!

See here for the printable puzzle with further explanations and here for a video including the solutions (that are known so far …).

University of Southampton are running a National Cipher Challenge.

Introduction to some of the ciphers that will be used is here.

Competition is https://www.cipherchallenge.org/

There is a great set of tools to use:

https://www.cipherchallenge.org/tools/

Please sign up for the challenge!

Contact Mrs Fleming on [email protected] if you need the monitoring pin to complete the registration.