Area and Circumference Practice

Front

What is the formula for the area of a circle?

Back

Area = πr², where r is the radius of the circle.

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2πr or Circumference = πd, where d is the diameter.

Front

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

Back

Radius = Diameter / 2 = 10 cm / 2 = 5 cm.

Front

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

Back

Area = π(5 cm)² = 25π cm² or about 78.5 cm².

Front

What is the diameter of a circle with a radius of 6 cm?

Back

Diameter = 2 × Radius = 2 × 6 cm = 12 cm.

Front

If the radius of a circle is doubled, how does the area change?

Back

The area increases by a factor of four (Area = π(2r)² = 4πr²).

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

What is the area of a circle with a radius of 12 inches?

Back

Area = π(12 in)² = 144π in² or about 452.16 in².

Front

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

Back

Radius = Circumference / (2π) = 31.4 cm / (2π) ≈ 5 cm.

Front

What is the circumference of a circle with a diameter of 7 cm?

Back

Circumference = π × Diameter = π × 7 cm ≈ 21.99 cm.