This is the perimeter of a rectangle and the perimeter of this circle.

25.12 ÷∈ 2 = 4cm

This is the radius of the circle, and ∏ is the pi, which is about 3. 14.

4×4×∏=50.24 square centimeters

This is the area of a circle.

Area of circle = radius × radius ×∈

* Read pai (the fourth sound)