Puzzles
Circles
Which is largest, the red or the blue area?
Show answer & extension
Hide answer & extension
Let \(4x\) be the side length of the square. This means that the radius of the red circle is \(2x\) and the radius of a blue circle is \(x\). Therefore the area of the red circle is \(4\pi x^2\).
The area of one of the blue squares is \(\pi x^2\) so the blue area is \(4\pi x^2\). Therefore the two areas are the same.
Extension
Is the red or blue area larger?
![](javascript:showlimage("circles.png"))
![](javascript:showlimage("circles-ext.png"))
