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Square Number Surprises
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Square number surprises

14 to 16
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There are unexpected discoveries to be made about square numbers...

Who's who?
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Who's who?

11 to 16
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Can you solve the clues to find out who's who on the friendship graph?

Pentagon Construction
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Pentagon construction

16 to 18
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Follow the instructions to create a regular pentagon. Can you prove it is indeed regular?
Window frames
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Window frames

5 to 14
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This task encourages you to investigate the number of edging pieces and panes in different sized windows.

Got It
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Got it

7 to 14
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A game for two people, or play online. Given a target number, say 23, and a range of numbers to choose from, say 1-4, players take it in turns to add to the running total to hit their target.

Children's Mathematical Writing
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Children's mathematical writing

5 to 11
Bernard Bagnall discusses the importance of valuing young children's mathematical representations in this article for teachers.
Weekly Challenges are here!
article

Weekly challenges are here!

11 to 18
Weekly challenges are here for NRICH! To celebrate this event, we've collected a set of 20 essential problems for you to try.
The Knapsack Problem and Public Key Cryptography
article

The knapsack problem and public key cryptography

16 to 18
An example of a simple Public Key code, called the Knapsack Code is described in this article, alongside some information on its origins. A knowledge of modular arithmetic is useful.
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