Area of Circles
Circle area depends on radius and pi. The formula is A = pi r squared.
Do this: Read the concept below, then try the quiz or activity.
Lesson 152 of 190
79%
Concept
Formula: A = πr^2
Where r is radius.
Examples: - r = 5 -> A = 25π ≈ 78.5 - d = 12 means r = 6 -> A = 36π ≈ 113.1
Units are square units. If radius doubles, area becomes 4 times as large.
Try it
Find the area: 1. r = 3 2. r = 10 3. d = 14 4. r = 2.5 5. A circle has area 49π. What is r?