Area and Circumference

Front

What is the formula for 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

How do you calculate the diameter of a circle if you know the circumference?

Back

Diameter can be calculated using the formula d = C/π.

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

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

Back

Radius can be found using the formula r = d/2.

Front

What is the relationship between diameter and radius?

Back

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

Front

If a circle has a radius of 3 cm, what is its area?

Back

A = π(3)² = 28.27 cm² (approximately).

Front

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

Back

r = C/(2π) = 31.4/(2π) = 5 cm.

Front

What is the circumference of a circle with a radius of 7 inches?

Back

C = 2π(7) = 43.98 inches (approximately).

Front

How do you convert from area to radius for a circle?

Back

To find the radius from the area, use r = √(A/π).

Front

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

Back

First find the radius: r = 10/2 = 5 cm. Then, A = π(5)² = 78.54 cm² (approximately).