Circumference and Area of Circles

Front

What is the formula for the circumference of a circle?

Back

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

Front

What is the formula for the area of a circle?

Back

A = πr², where r is the radius.

Front

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

Back

5 cm (radius is half of the diameter).

Front

What is the value of π (pi) commonly approximated as?

Back

3.14 or 22/7.

Front

How do you find the circumference of a circle with a radius of 7 inches?

Back

C = 2πr = 2 × 3.14 × 7 = 43.96 inches.

Front

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

Back

A = πr² = 3.14 × 4² = 50.24 square inches.

Front

What is the relationship between diameter and radius?

Back

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

Front

How do you calculate the area of a circle with a diameter of 12 cm?

Back

First find the radius (r = 6 cm), then A = πr² = 3.14 × 6² = 113.04 cm².

Front

What is the circumference of a circle with a diameter of 20 feet?

Back

C = πd = 3.14 × 20 = 62.8 feet.

Front

If a circular garden has a radius of 3 meters, what is its area?

Back

A = πr² = 3.14 × 3² = 28.26 m².