Calculate the area of circles
Given the radius or diameter of a circle, we can calculate it's area.
Given a radius r, the area of a circle is calculated as:
Area = π x Radius²
Given a diameter d, the area of a circle is calculated as:
Area = π x (Diameter/2)²
For instance, if we have a circle with a radius of 1 mm, the area A of the circle to two decimal places will be:
A = π x 1² = 3.14 mm²
If we have a circle with a diameter of 12 cm, the area A of the circle to two decimal places will be:
A = π x (12/2)² = π x 36 = 113.10 cm²
Below is a table showing the first 6 question answer pairs for the topic "Area of circles" as used in the lessons for this topic. Our games and tests for the topic use these 6 items plus 10 additional question answer pairs.
Each of our math topics for secondary are made up of between 6 and 20 question and answer pairs (both the written form and a robot voice speaking those questions and answers). Each topic can be used with all the activities on the site.