Circumference & Area of Circles & Semi-Circles

Front

What is the formula for the circumference of a circle?

Back

The circumference (C) of a circle is calculated using the formula: C = πd, where d is the diameter of the circle.

Front

How do you calculate the area of a circle?

Back

The area (A) of a circle is calculated using the formula: A = πr², where r is the radius of the circle.

Front

What is the relationship between diameter and radius?

Back

The diameter (d) of a circle is twice the radius (r): d = 2r.

Front

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

Back

C = 2πr = 2π(7) ≈ 43.98 cm.

Front

If the diameter of a circle is 14 cm, what is its area?

Back

A = πr² = π(7)² ≈ 153.86 cm².

Front

What is the formula for the area of a semicircle?

Back

The area (A) of a semicircle is calculated using the formula: A = (1/2)πr².

Front

How do you find the circumference of a semicircle?

Back

The circumference (C) of a semicircle is calculated using the formula: C = πr + d, where d is the diameter.

Front

What is the circumference of a cookie with a radius of 5 inches?

Back

C = 2πr = 2π(5) ≈ 31.4 inches.

Front

What is the area of a semicircle with a radius of 5 inches?

Back

A = (1/2)πr² = (1/2)π(5)² ≈ 39.27 inches².

Front

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

Back

r = C/(2π) = 31.4/(2π) ≈ 5 cm.