Circumference and Area of Circles

Front

What is the formula for the area of a circle?

Back

Area = πr², where r is the radius.

Front

What is the formula for the circumference of a circle?

Back

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

Front

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

Back

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

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

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

Back

Circumference = 2π(7) ≈ 43.98 cm.

Front

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

Back

Area = π(5)² ≈ 78.54 cm².

Front

What is the distance around a circle called?

Back

Circumference.

Front

What is the distance from the center of a circle to any point on its edge called?

Back

Radius.

Front

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

Back

The area increases by a factor of four.

Front

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

Back

Diameter = 2 × Radius = 2 × 12 = 24 inches.