Finding Area and Circumference of Circle

Front

What is the formula for the area of a circle?

Back

Area = π × r², where r is the radius.

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2 × π × r or Circumference = π × d, where d is the diameter.

Front

What is the radius of a circle?

Back

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

Front

What is the diameter of a circle?

Back

The diameter is the distance across the circle through its center, equal to twice the radius.

Front

If the radius of a circle is 9 inches, what is the diameter?

Back

Diameter = 2 × radius = 2 × 9 in = 18 in.

Front

If the diameter of a circle is 14 cm, what is the radius?

Back

Radius = Diameter / 2 = 14 cm / 2 = 7 cm.

Front

What is the area of a circle with a radius of 15 ft?

Back

Area = π × (15 ft)² ≈ 706.86 ft².

Front

What is the circumference of a circle with a diameter of 10 m?

Back

Circumference = π × 10 m ≈ 31.42 m.

Front

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

Back

First, find the radius by dividing the diameter by 2, then use the area formula: Area = π × r².

Front

What is the relationship between radius and diameter?

Back

The diameter is always twice the length of the radius.