Codebreakers
Calling all maths detectives!
Can you solve the mysteries hidden in our carefully selected NRICH tasks?
Can you solve the mysteries hidden in our carefully selected NRICH tasks?
This article for Primary and Secondary teachers is all about the mathematics behind solving puzzles, unravelling mysteries and breaking codes.
Count the Digits Age 5 to 11Challenge Level 
Age 5 to 11
Challenge Level
In this investigation we are going to count the number of 1s, 2s, 3s etc in numbers. Can you predict what will happen?
I Like ... Age 5 to 7Challenge Level
Age 5 to 7
Challenge Level
Mr Gilderdale is playing a game with his class. What rule might he have chosen? How would you test your idea?
Secret Number Age 5 to 7Challenge Level
Age 5 to 7
Challenge Level
Annie and Ben are playing a game with a calculator. What was Annie's secret number?
What Number? Age 5 to 7 ShortChallenge Level
Age 5 to 7
ShortChallenge Level
I am less than 25. My ones digit is twice my tens digit. My digits add up to an even number.
Number Detective Age 5 to 11Challenge Level
Age 5 to 11
Challenge Level
Follow the clues to find the mystery number.
Coded Hundred Square Age 7 to 11Challenge Level
Age 7 to 11
Challenge Level
This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?
Mystery Matrix Age 7 to 11Challenge Level
Age 7 to 11
Challenge Level
Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.
Curious Number Age 7 to 11Challenge Level
Age 7 to 11
Challenge Level
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?
Satisfying Four Statements Age 7 to 11Challenge Level
Age 7 to 11
Challenge Level
Can you find any two-digit numbers that satisfy all of these statements?