By Mike McRae, 8 April 2025
Alice forgot the code to get into her computer. She knows it was a number with three digits, like 286 or 935. All she can remember is that the first digit is the second digit minus 3. The second digit is 4 times the third digit. And two of the digits are the same. Can you help Alice get into her computer?
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By Ariel Marcy, 12 March 2024
Lavonne is testing a secret code with her friend Jack. First, she picks 3 different secret numbers between 1 and 9. Then she finds the sum of each pair of numbers. Lavonne wants to know if Jack can figure out the original secret numbers just from the sums?
By David Shaw, 12 December 2018
If you’re sitting there twiddling your thumbs, see if you can decode this message. If you need a hint, you can always phone a friend! 3666882255533 443355544499 339987772
By David Shaw, 21 March 2018
You’ve just received a secret coded message: AD, BA, BH, CE, DB, DI, EF You know it follows a pattern, but can you work out what pair of letters come next?
By David Shaw, 3 March 2015
Learn the Caesar cipher, one of the oldest codes ever devised!
By David Shaw, 13 January 2014
Written by Gabrielle Tramby In this activity you’ll do maths like a computer. It’s a bit tricky, so younger readers may want to read the ‘What’s Happening?’ section first.