Area and Circumference of a 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

If a circle has a radius of 7 cm, what is its area?

Back

Area = π × (7)² = 153.94 cm² (using π ≈ 3.14).

Front

If a circle has a diameter of 10 m, what is its circumference?

Back

Circumference = π × d = 3.14 × 10 = 31.4 m.

Front

What is the relationship between diameter and radius?

Back

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

Front

How do you convert diameter to radius?

Back

Radius = Diameter ÷ 2.

Front

What is the area of a circle with a diameter of 4 feet?

Back

Area = π × (2)² = 12.56 ft².

Front

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

Back

Circumference = 2 × π × 3 = 18.84 inches.

Front

If the area of a circle is 78.5 m², what is the radius?

Back

Radius = √(Area/π) = √(78.5/3.14) ≈ 5 m.

Front

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

Back

Area = π × (10)² = 314 cm².