Circumference & Area of a Circle

POINT

円周は直径×π、面積は半径×半径×πです。直径が与えられたら、まず半径を求めましょう。

Example

Find the circumference and area of the following circle.

Practice

Find the circumference and area of each circle.

Radius = 5 cm

Circumference: 10π cm
Area: 25π cm²

Radius = 8 cm

Circumference: 16π cm
Area: 64π cm²

Diameter = 12 cm

Circumference: 12π cm
Area: 36π cm²

Diameter = 18 cm

Circumference: 18π cm
Area: 81π cm²