Lesson 9: The Circle

A trundle wheel, used to measure distances, has a radius of eight inches. How many feet has it traveled on the ground when it has made 300 revolutions?

1,256'

If the radius of a circle is 2.5 meters, what is the circumference?

15.7 m

A 40-foot, class 2 pole has a minimum top circumference of 50 inches. What is its minimum diameter?

15.92"

Find the area of a circle that has a radius of seven inches.

153.86 in2

The butt of a pole has a diameter of 50 inches. What is its circumference?

157.0"

What radius, in millimeters, is needed on a trundle wheel so that one rotation will measure a distance of one meter?

159.2 mm

If the diameter of a circle is 32 inches, what is the radius?

16"

If the radius of a circle is nine centimeters, what is the diameter?

18.0 cm

A full reel of cable has a diameter of 60 inches. A job requires 314 feet of cable. How many turns of cable should be taken off the reel?

20 turns

A circle has a diameter of 18 centimeters. What is the area of the circle?

254.3 cm2

If the circumference of a circle is 85 millimeters, what is the diameter?

27.1 mm

A circle has a diameter of five inches and a circumference of 15.71 inches. What is the ratio of the circumference to the diameter?

3.142

Which equation shows the correct relationship between the radius and the area of a circle?

A = πr2

The diameter of a circle is always 3.14 times its circumference.

False

The radius of a circle is equal to twice its diameter.

False

In many calculations, 3.14 or 3 1/7 are typically used to approximate π.

True

The diameter of a circle is equal to twice its radius.

True

A circle is a set of all points in a plane that are all the same distance from a common point called the ? .

center

The distance around a circle is called the ? .

circumference

Which equation shows the correct relationship between the radius and the diameter of a circle?

d = 2r

Which equation shows the correct relationship between the diameter and the circumference of a circle?

d = C/π

The length of any line segment that connects two points on the circle and passes through the center is called the ? .

diameter

The ratio of the circumference of a circle to the ? is represented by the Greek letter π.

diameter

The distance from the center of the circle to any point on the circle is called the ? .

radius