Parts of a Circle

Circles

Parts of a Circle, Pi, Circumference, and Area

Parts of a Circle

• Radius: line segment that goes from the center to the edge of the circle (HALF the DIAMETER)

• Diameter: line segment that goes from edge to edge on a circle (TWICE the RADIUS)

• Circumference: the distance around the outside of a circle (AKA perimeter)

Multiple Choice

A pond has a diameter of 12 feet. What is its radius?

• 12 feet

• 6 feet

• 24 feet

Multiple Choice

A tire has a radius of 14 inches. What is its diameter?

• 14 inches

• 7 inches

• 28 inches

Circumference

• There are two fomulas for finding circumference

• C = πd

• C = 2πr

• Circumference is a little more than 3 times the diameter

Relationship Between Diameter and Circumference

https://kera.pbslearningmedia.org/resource/ng09.math.geometry.pla.diameter/relationship-between-diameter-and-circumference/

What is Pi?

• the ratio of the circumference to the diameter of a circle (π= c/d)

• a greek symbol (π)

• approximately 3.14

• used when solving area and circumference of circles

Multiple Select

What is pi?

Check ALL applicable answers!

• a delicious dessert

• the ratio between circumference and diameter

• a Greek symbol

• exactly 3.14

• approximately 3.14

Multiple Choice

A cruise ship has a large, circular window with a diameter of 6 meters. Approximately what is the window's circumference?

• 18 meters

• 12 meters

• 19 meters

• 6 meters

Multiple Choice

The radius of the circle is 9 meters. What is the circle's circumference?

• 56.52 m

• 28.26 m

• 18 m

Area

• the measure inside the circle

• always in square units

• A = πr²

• https://www.youtube.com/watch?v=YokKp3pwVFc

Multiple Choice

What is the area of this circle?

• 28.26 cm²

• 28.26 cm

• 9.42 cm²

• 9.42 cm

Multiple Choice

What is the area of this circle? Round to the nearest tenths place.

• 452.2 cm²

• 113.1 cm²

• 37.7 cm²

Circumference Word Problem

Multiple Choice

If you pedal for 35 rotations, how far did you travel?

• 78.5 in

• 2,747.5 in

• 113.5 in

• 1,962.5 in

Area Word Problem

Multiple Choice

How much of the lawn does not get watered by the sprinkler?

• 86 sq ft

• 714 sq ft

• 314 sq ft

• 400 sq ft

Word Cloud

What are your feelings of circle formulas?