Area & 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 5 inches, what is the area?

Back

Area = π × (5)² = 78.5 in² (approximately).

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 circumference of a circle with a radius of 10 cm?

Back

Circumference = 2 × π × 10 cm = 62.83 cm (approximately).

Front

What is the area of a circle with a diameter of 12 cm?

Back

Area = π × (6)² = 113.1 cm² (approximately).

Front

What do you need to calculate the circumference of a circle?

Back

You need the radius or diameter of the circle.

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

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

Back

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

Front

What is the area of a circle with a radius of 3 inches?

Back

Area = π × (3)² = 28.27 in² (approximately).