Codebreakers

This article for Primary and Secondary teachers is all about the mathematics behind solving puzzles, unravelling mysteries and breaking codes.

In this investigation we are going to count the number of 1s, 2s, 3s etc in numbers. Can you predict what will happen?

Mr Gilderdale is playing a game with his class. What rule might he have chosen? How would you test your idea?

Annie and Ben are playing a game with a calculator. What was Annie's secret number?

I am less than 25. My ones digit is twice my tens digit. My digits add up to an even number.

Follow the clues to find the mystery number.

This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?

Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.

Can you order the digits from 1-3 to make a number which is divisible by 3 so when the last digit is removed it becomes a 2-figure number divisible by 2, and so on?

Can you find any two-digit numbers that satisfy all of these statements?