Area and Circumference of a Circle

Front

What is the formula for the circumference of a circle?

Back

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

Front

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

Back

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

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × radius.

Front

If the diameter of a circle is 20 inches, what is the radius?

Back

Radius = diameter ÷ 2 = 20 inches ÷ 2 = 10 inches.

Front

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

Back

Area = π × (radius)² = π × (5 m)² ≈ 78.54 m².

Front

How do you convert radius to diameter?

Back

Multiply the radius by 2.

Front

What is the circumference of a circle with a radius of 10 m?

Back

Circumference = 2 × π × 10 m ≈ 62.83 m.

Front

What is the formula for the area of a circle?

Back

Area = π × (radius)².

Front

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

Back

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

Front

What is π (pi)?

Back

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