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Why does circle area formula work?

Melissas Skirrow and Julia Geerkens 06/03/09

+Problem

“ why does the circle area formula work?”

The formula for a rectangle is… A = L x W

The formula for a circle is… A = πr2

+Process

Firstly we cut out our circle and pasted it into a rectangle.

We then found the area of the rectangle.

We measured the radius and circumference of our circle.

We measured the length and width of our rectangle, that is when we dicovered that the width and radius were the same.

We also discovered that the length was half the size of the circumference.

Using this we found a formula.

+challenges

Some challenges we faced were;

Using the information gathered to find the formula.

Another challenge was using only pi and radius.

+solution

A = L x W

A = C/2 x r

A = πD/2 x r

A = π2r/2 x r

A = πr x r

A = πr2