Area and Circumference 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 relationship between diameter and radius?

Back

The radius is half of the diameter. Formula: r = d/2.

Front

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

Back

5 inches.

Front

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

Back

3.14.

Front

How do you calculate the diameter if you know the circumference?

Back

Diameter = Circumference / π.

Front

If the circumference of a circle is 31.4 inches, what is the diameter?

Back

10 inches.

Front

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

Back

25.12 inches (C = 2πr = 2 * 3.14 * 4).

Front

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

Back

A = πr².

Front

If the radius of a circle is 3 inches, what is its area?

Back

28.26 square inches (A = π * 3² = 3.14 * 9).

Front

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

Back

14 inches (d = 2r).