Measuring Circles

Front

What is the diameter of a circle?

Back

The diameter is the distance across a circle through its center, equal to twice the radius.

Front

What is the radius of a circle?

Back

The radius is the distance from the center of the circle to any point on its circumference.

Front

How do you calculate the circumference of a circle?

Back

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

Front

What is the value of π (pi)?

Back

π is approximately equal to 3.14.

Front

If a circle has a radius of 5 cm, what is its diameter?

Back

Diameter = 2 × radius = 2 × 5 cm = 10 cm.

Front

What is the area of a circle?

Back

Area = π × radius².

Front

If a circle has an area of 78.5 cm², what is its radius?

Back

Radius = √(Area/π) = √(78.5/3.14) ≈ 5 cm.

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the length of the radius.

Front

How do you find the circumference of a circle with a radius of 7 cm?

Back

Circumference = 2 × π × 7 cm ≈ 43.96 cm.

Front

What is the approximate difference in circumference between a circle with a diameter of 4 cm and one with a diameter of 10 cm?

Back

Difference = Circumference of larger circle - Circumference of smaller circle = (π × 10) - (π × 4) = 6π ≈ 18.85 cm.