# Radius, diameter, and circumference and area of Circles

Home | Online Math Tutoring | 7th Grade Math Tutoring | **Radius, diameter, and circumference and area of Circles**

A circle is a plane round figure in which all points are equidistant from the center.

Radius is a line segment that joins the center of circle to any point on the circumference of circle.

Diameter is a straight line segment passing through the center of circle, the endpoints of which touches the circumference of circle.

Circumference of circle is the distance around the circle.

Circumference of circle = 2π× radius = π× diameter

Area of circle = π× (radius)^{2}

*Example:*What is the radius of circle with diameter 12 inches?

Radius of circle = = = 6 inches

*Example:*If the circumference of circle is 88 cm, then what is the radius of circle? (Use π= )

2π*r* = 88

2 ××*r* = 88 implies *r* = 14 cm

#### Check Point:

- What is the radius of circle with circumference 24π in?
- What is the area of circle with circumference 30.2 yards? Round your answer to the nearest tenth. (Use π = 3.14)
- What is the area of circle with diameter 6 yards? Round your answer to the nearest tenth. (Use π = 3.14)
- What is the diameter of circle with circumference 63 feet? Round your answer to the nearest whole. (Use π = 3.14)
- What is the circumference of circle with area 12.6 in
^{2}? Round your answer to the nearest tenth. (Use π = 3.14)

##### Answer key

- 12 in.
- 6 yd
^{2} - 3 yd
^{2} - 20 feet
- 6 in

*Download/Solve a **Worksheet** for Radius, Diameter, Circumference and Area of Circles*

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