Area and Circumference of Circles

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

If the radius of a circle is 10 meters, what is the area?

Back

Area = π × (10)² = 314.16 square meters.

Front

If the diameter of a circle is 20 meters, what is the radius?

Back

Radius = Diameter / 2 = 20 / 2 = 10 meters.

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

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

Back

Radius = Circumference / (2 × π) = 31.4 / (2 × 3.14) = 5 cm.

Front

What is the area of a circle with a radius of 5 cm?

Back

Area = π × (5)² = 78.5 square cm.

Front

What does the term 'circumference' refer to?

Back

Circumference is the distance around the circle.

Front

What does the term 'radius' refer to?

Back

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

Front

What does the term 'diameter' refer to?

Back

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