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Königsberg
Age 11 to 14
Challenge Level 
Try drawing these maps without lifting your pencil
What do you notice about the start and end positions?
- Now consider these
What do you notice about the start and end positions now?
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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!
Summing Consecutive Numbers
15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?