Circles

Front

What is a circle?

Back

A circle is a shape consisting of all points in a plane that are at a given distance from a fixed point, called the center.

Front

What is the center of a circle?

Back

The center of a circle is the fixed point from which all points on the circle are equidistant.

Front

What is a radius?

Back

A radius is a line segment from the center of the circle to any point on the circle.

Front

What is a diameter?

Back

A diameter is a line segment that passes through the center of the circle and has its endpoints on the circle. It is twice the length of the radius.

Front

How do you calculate the circumference of a circle?

Back

Circumference (C) = π × diameter (d) or C = 2 × π × radius (r).

Front

What is the formula for the area of a circle?

Back

Area (A) = π × radius² (r²).

Front

If the radius of a circle is 5 cm, what is the diameter?

Back

Diameter = 2 × radius = 2 × 5 cm = 10 cm.

Front

If the diameter of a circle is 12 cm, what is the radius?

Back

Radius = diameter / 2 = 12 cm / 2 = 6 cm.

Front

What is the circumference of a circle with a radius of 4 cm?

Back

Circumference = 2 × π × 4 cm = 8π cm.

Front

What is the area of a circle with a radius of 3 cm?

Back

Area = π × (3 cm)² = 9π cm².