Area and circumference of circles

Front

What is the formula to calculate the radius of a circle if the diameter is known?

Back

Radius = Diameter / 2

Front

If the radius of a circle is 10 ft, what is the formula to find the diameter?

Back

Diameter = 2 * Radius

Front

Define the term 'diameter' in relation to a circle.

Back

The diameter is the longest distance across the circle, passing through the center, and is twice the length of the radius.

Front

What is the formula for calculating the circumference of a circle?

Back

Circumference = π * Diameter or Circumference = 2 * π * Radius

Front

How do you calculate the circumference of a circle with a radius of 6 cm?

Back

Circumference = 2 * π * 6 cm ≈ 37.70 cm.

Front

What is the relationship between the radius and diameter of a circle?

Back

The diameter is always twice the length of the radius.

Front

What is the formula for calculating the area of a circle?

Back

Area = π * Radius²

Front

How do you find the area of a semicircle with a diameter of 18 cm?

Back

Area = (π * (Diameter/2)²) / 2 = (π * (9 cm)²) / 2 ≈ 127.17 cm².

Front

What is the value of π (pi) approximately?

Back

π (pi) is approximately 3.14.

Front

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

Back

Radius = Circumference / (2 * π) = 31.4 cm / (2 * 3.14) ≈ 5 cm.