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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$$\pi \cdot$$(radius)2 usually expressed as $$\pi \cdot r^2$$ where r is the radius of a circle.
The area of a circle is all the space inside a circle's circumference.
 In the picture on the left, the area of the circle is the part of the circle that is changing color.

Explore and discover the relationship bet wen the area formula , the radius of a circle and its graph with with our interactive applet
Practice Problems

Problem 1)

What is the area of the circle on the left?

Problem 2

What is this circle's area?

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

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)

Problem 5
What is the diameter of a circle if its area is 360 in2? (Round your answer to the nearest hundredth of an inch)

Challenge Problems

Problem 6

A circle has a diameter of 12 inches. What is its area in terms of $$\pi$$ . (Need a hint)