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Choose any three by three square of dates on a calendar page...

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Adding All Nine

Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!

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Pyramids

What are the missing numbers in the pyramids?

Königsberg

Age 11 to 14 Challenge Level:

You may like to download these notes which help to explain the diagrammatic representation and provides blank diagrams and maps with no bridges for further investigation.

This lesson plan suggests how you could introduce this problem in the classroom.