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'Disappearing Square' printed from http://nrich.maths.org/

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Do you know how to find the area of a triangle?

You can count the squares.

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What happens if we turn the triangle on end? Press the button and see.

Try counting the number of units in the triangle now.

Do you have any interesting findings to report?

The area of a triangle can be found by multiplying half the base by the height. What is the area of this whole triangle?

Triangle.

Now find the areas of the shapes marked A, B and C.

If you add these answers together, would they equal the same as the whole triangle? Try and see.

Do you have any interesting findings to report?