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If you are not sure what a triangular number is, take a look at Picturing Triangular Numbers
You might find it useful to record each person's numbers on a 1 to 100 grid.
Satisfying Statements
Age 11 to 14
Challenge Level 
If you are not sure what a triangular number is, take a look at Picturing Triangular Numbers
You might find it useful to record each person's numbers on a 1 to 100 grid.
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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!
