Circumference and Area of Circles

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 the radius of a circle is 7 cm, what is the circumference?

Back

Circumference = 2 × π × 7 cm ≈ 43.98 cm.

Front

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

Back

Radius = Diameter ÷ 2 = 10 inches ÷ 2 = 5 inches.

Front

What is the relationship between radius and diameter?

Back

Diameter = 2 × Radius.

Front

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

Back

Radius = Circumference ÷ (2 × π) ≈ 5 cm.

Front

What does π (pi) represent in circle calculations?

Back

π (pi) is a constant approximately equal to 3.14, representing the ratio of the circumference of a circle to its diameter.

Front

If a circle has a radius of 3 m, what is its area?

Back

Area = π × (3 m)² ≈ 28.27 m².

Front

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

Back

Circumference = π × 12 cm ≈ 37.68 cm.

Front

How do you convert diameter to radius?

Back

Divide the diameter by 2.