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What do you know about the number 1? Where would it go?
How about the number 1? And 3?
You could look at all the odd numbers first, for example, and decide where they go in the diagram.
Arrange the numbers 1 to 6 in each set of circles below. The sum of each side of the triangle should equal the number in its centre.
Pat counts her sweets in different groups and both times she has some left over. How many sweets could she have had?