Circumference and 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

What does the radius of a circle represent?

Back

The radius is the distance from the center of the circle to any point on its circumference.

Front

Define the diameter of a circle.

Back

The diameter is a line segment that passes through the center of the circle and connects two points on its circumference. It is twice the length of the radius.

Front

How do you calculate the area of a circle if the diameter is known?

Back

First, find the radius by dividing the diameter by 2, then use the formula A = πr².

Front

What is the circumference of a circle?

Back

The circumference is the distance around the circle, calculated using the formula C = 2πr or C = πd, where d is the diameter.

Front

If a circle has a radius of 5 inches, what is its area?

Back

A = π(5)² = 25π ≈ 78.54 square inches.

Front

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

Back

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

Front

How do you convert the diameter of a circle to its radius?

Back

To find the radius, divide the diameter by 2 (r = d/2).

Front

What is the area of a circle with a radius of 10 meters?

Back

A = π(10)² = 100π ≈ 314.16 square meters.

Front

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

Back

Using the formula C = 2πr, the radius r = C/(2π) = 31.4/(2π) ≈ 5 meters.