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Area of a Circle and its formula

Practice Problems & examples

Formula for Area of circle:

The formula to find a circle's area : π×(radius)2 usually expressed as Πr2 where r is the radius of a circle.
The area of a circle is all the space inside a circle's circumference.
play pause
area of circle demo


In the picture on the left, the area of the circle is the part of the circle that is changing color.


applet

Interactive Area of a Circle

(View applet on its own page)
Explore and discover the relationship between area, radius and graph of a circle. . Just click and drag the points.
Radical Form?
$$ Area = \pi \cdot radius^2 $$
$$ $$



Practice Problems

Problem 1) Circle's Area

What is the area of the circle on the left?
Answer


Problem 2
Area of Circle Two
What is this circle's area?
Answer


Problem 3
What is the area of a circle with a radius of 7 centimeters?
Answer


Problem 4
What is the radius of a circle if its area is 120 in2? (Round your answer to the nearest hundredth of an inch)
Answer
challenge problems

Challenge Problems

Problem 5

A circle has a diameter of 12 inches. Calculate its area. (Need a hint)
Answer


Problem 6

If a circle's radius is doubled, then how much did its area increase?
Answer