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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!
Age 11 to 14
Challenge Level
Can a number be both odd and even?
What does this tell you about where the ODD NUMBER and EVEN NUMBER headings have to go?
Can you use this idea to position any of the other heading cards?
If you have reached a stage where you have placed most of the numbers but have a few that you cannot place, don't panic!
Could you swap one of the numbers that you can't place for a number that is already on the grid?
You might be able to swap them and then find that the number you have removed can be placed on one of the empty squares.
Don't forget: $1$ is not a prime number!
Triangle numbers can be represented by a triangular array of squares
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NRICH is part of the family of activities in the Millennium Mathematics Project.
NRICH is part of the family of activities in the Millennium Mathematics Project.