Circumference and Area of Circles

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2πr, where r is the radius.

Front

What is the formula for the area of a circle?

Back

Area = πr², where r is the radius.

Front

If the radius of a circle is 4 units, what is the circumference?

Back

Circumference = 2π(4) = 8π units.

Front

If the radius of a circle is 4 units, what is the area?

Back

Area = π(4)² = 16π square units.

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 find the area of a sector?

Back

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

Front

What is an arc in a circle?

Back

An arc is a part of the circumference of a circle.

Front

If the length of an arc is 7.85 units and the radius is 4 units, how do you find the angle in degrees?

Back

θ = (arc length / circumference) × 360 = (7.85 / (2π(4))) × 360.

Front

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

Back

Diameter = 2 × radius.

Front

What is the area of a circle with a diameter of 10 units?

Back

Area = π(5)² = 25π square units.