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Cracking Codes

When a secret agent wants to send a message, they write it in code so their enemies can't read it. Codebreakers need to develop mathematical skills like working backwards, being systematic, and ruling out possibilities in order to crack enemy codes and save the day. These problems will give you the chance to train your brain in order to become a better code cracker!
Satisfying Statements
problem

Satisfying Statements

Age
11 to 14
Challenge level
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Can you find any two-digit numbers that satisfy all of these statements?
Statement Snap
problem
Favourite

Statement Snap

Age
7 to 14
Challenge level
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You'll need to know your number properties to win a game of Statement Snap...
Charlie's delightful machine
problem
Favourite

Charlie's delightful machine

Age
11 to 16
Challenge level
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Here is a machine with four coloured lights. Can you develop a strategy to work out the rules controlling each light?

Placeholder: several colourful numbers
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Number Teasers

Age
11 to 16
Challenge level
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Some tricky number teasers for you to puzzle over
Placeholder: several colourful numbers
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Hidden Treasures

Age
11 to 16
Challenge level
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Try these treasures to celebrate NRICH's birthday!