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

Back

Radius = Diameter / 2 = 10 cm / 2 = 5 cm.

Front

Calculate the area of a circle with a radius of 3 m.

Back

Area = π × (3 m)² = 28.27 m² (approximately).

Front

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

Back

Circumference = 2 × π × 4 in = 25.13 in (approximately).

Front

If the area of a circle is 50.27 cm², what is the radius?

Back

Radius = √(Area / π) = √(50.27 cm² / π) ≈ 4 cm.

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

A circle has a circumference of 31.4 m. What is its diameter?

Back

Diameter = Circumference / π = 31.4 m / π ≈ 10 m.

Front

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

Back

Area = π × (6 ft)² = 113.1 ft² (approximately).

Front

If a circle's radius is doubled, how does its area change?

Back

The area increases by a factor of 4.