Circle Measurements and Formulas

Front

What is the formula for the area of a circle?

Back

Area = πr², where r is the radius of the circle.

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2πr, where r is the radius of the circle.

Front

What is a sector of a circle?

Back

A sector is a portion of a circle enclosed by two radii and the arc between them.

Front

How do you calculate the area of a sector?

Back

Area of a sector = (θ/360) × πr², where θ is the angle in degrees and r is the radius.

Front

What is the relationship between the radius and diameter of a circle?

Back

Diameter = 2 × Radius.

Front

What is the formula for the length of an arc?

Back

Length of an arc = (θ/360) × 2πr, where θ is the angle in degrees and r is the radius.

Front

If a circle has a radius of 5 units, what is its area?

Back

Area = π(5)² = 25π units².

Front

If a circle has a diameter of 10 units, what is its circumference?

Back

Circumference = 2π(5) = 10π units.

Front

What is the area of a circle with a radius of 4 inches?

Back

Area = π(4)² = 16π in².

Front

How do you find the radius if the area of a circle is 36π square units?

Back

Radius = √(Area/π) = √(36) = 6 units.