Circles - Circumference and Area

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2 × π × r (where r is the radius) or Circumference = π × d (where d is the diameter).

Front

What is the formula for the area of a circle?

Back

Area = π × r² (where r is the radius).

Front

If a circle has a radius of 1.5 feet, what is its circumference?

Back

Circumference = 2 × π × 1.5 ≈ 9.42 feet.

Front

If a circle has a diameter of 3.5 feet, what is its circumference?

Back

Circumference = π × 3.5 ≈ 10.99 feet.

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

How do you convert circumference to diameter?

Back

Diameter = Circumference / π.

Front

What is the approximate value of π?

Back

π ≈ 3.14.

Front

If a circle has a circumference of 157 cm, what is its diameter?

Back

Diameter = Circumference / π ≈ 157 / 3.14 ≈ 50 cm.

Front

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

Back

Area = π × 5² ≈ 78.5 square inches.

Front

What is the area of a semicircle with a diameter of 36 inches?

Back

Area = (π × (18)²) / 2 ≈ 508.68 square inches.