Circumference and Area of Circles

Front

What is the formula to calculate the circumference of a circle?

Back

Circumference = π × diameter or Circumference = 2 × π × radius.

Front

If the radius of a circle is 10 cm, what is the diameter?

Back

Diameter = 2 × radius = 20 cm.

Front

What is the area of a circle with a radius of 7 cm?

Back

Area = π × radius² = 153.94 cm² (approximately).

Front

What is the value of π (pi) to two decimal places?

Back

π is approximately equal to 3.14.

Front

How do you find the radius if the diameter is known?

Back

Radius = diameter ÷ 2.

Front

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

Back

Area = π × (diameter/2)² = 113.10 m² (approximately).

Front

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

Back

Radius = Circumference ÷ (2 × π) = 5 m.

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the length of the radius.

Front

If the area of a circle is 78.5 cm², what is the radius?

Back

Radius = √(Area/π) = 5 cm (approximately).

Front

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

Back

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