Unit 3 Circles Review

Front

What is the formula for the circumference of a circle?

Back

C = 2πr, where C is the circumference and r is the radius.

Front

What is the formula for the area of a circle?

Back

A = πr², where A is the area and r is the radius.

Front

What is a radius of a circle?

Back

A radius is a line segment from the center of the circle to any point on its circumference.

Front

What is a diameter of a circle?

Back

A diameter is a line segment that passes through the center of the circle and has its endpoints on the circumference. It is twice the length of the radius.

Front

How do you find the radius if you know the circumference?

Back

Use the formula r = C/(2π), where C is the circumference.

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the length of the radius (d = 2r).

Front

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

Back

C = 2π(5) = 31.4 cm (approximately).

Front

If a circle has a circumference of 62.8 cm, what is its radius?

Back

r = C/(2π) = 62.8/(2π) = 10 cm.

Front

What is the perimeter of a semicircle with a diameter of 10 units?

Back

Perimeter = (1/2)πd + d = (1/2)π(10) + 10 = 5π + 10 (approximately 25.71 units).

Front

What is the area of a circle with a radius of 7 units?

Back

A = π(7)² = 49π (approximately 153.94 square units).