Review Area of Circles

Front

What is the formula for the area of a circle?

Back

A = πr², where A is the area and r is the radius.

Front

If a circle has a diameter of 10 feet, what is its radius?

Back

The radius is 5 feet, since the radius is half of the diameter.

Front

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

Back

The diameter is twice the radius (d = 2r).

Front

How do you calculate the circumference of a circle?

Back

C = πd or C = 2πr, where C is the circumference, d is the diameter, and r is the radius.

Front

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

Back

A = π(3)² = 28.26 cm².

Front

What is the area of a semicircle with a radius of 4 cm?

Back

A = (1/2)π(4)² = 25.13 cm².

Front

If the circumference of a circle is 31.4 cm, what is its radius?

Back

r = C/(2π) = 31.4/(2π) = 5 cm.

Front

What is the area of a circle with a diameter of 8 cm?

Back

A = π(4)² = 50.24 cm².

Front

What is the formula to find the area of a circle using the diameter?

Back

A = (π/4)d², where d is the diameter.

Front

How do you find the area of a circle if you only know the circumference?

Back

First, find the radius using r = C/(2π), then use A = πr².