Stage: 2 Challenge Level: 
Think of a number.
Square it.
Subtract your starting number.
Is the number you're left with odd or even?
Try with other numbers.
What do you notice?
How do these images help you explain your observations?
Practical Activity. Generalising. Working systematically. Interactivities. Cubes. Square numbers. Tangram. Visualising. Compound transformations. Odd and even numbers.
Published May 2004,October 2009.
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