Circle Area & Circumference

Front

What is the formula for the circumference of a circle?

Back

C = 2πr, where C is the circumference and r is the radius.

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 radius of 4, what is its circumference?

Back

8π or about 25.12.

Front

If a circle has a radius of 12 inches, what is its area?

Back

144π or about 452.16 in².

Front

What do you need to calculate to find out how much fencing is required for a circular playground?

Back

You need to calculate the circumference.

Front

What is the diameter of a circle if its radius is 5 inches?

Back

The diameter is 10 inches (D = 2r).

Front

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

Back

Use the formula r = C/(2π).

Front

What is the area of a circle with a diameter of 18 cm?

Back

254 cm².

Front

If Danielle wants to ice 3 cookies with a radius of 5 inches, how much area must she cover?

Back

235.5 in².

Front

What is the relationship between diameter and radius?

Back

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