Circles Reteach

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 = π r²

• 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?

• 28.26 in²

• 56.52 in²

• 254.34 in²

Multiple Choice

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

• 452.2 cm²

• 113.1 cm²

• 37.7 cm²

Finding Radius or Diameter when Given Circumference

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Multiple Choice

3.Find the diameter of a circle with a circumference of 25.12 inches.

• 8 inches

• 11 inches

• 4 inches

• 13 inches

Multiple Choice

4.Find the radius of a circle with a circumference of 423.9 inches.

• 67.5 inches

• 62.5 inches

• 167.5 inches

• 135 inches

Multiple Choice

5.Find the radius of a circle with a circumference of 59.66 feet.

• 19 feet

• 25.5 feet

• 13.5 feet

• 9.5 feet

Multiple Choice

6.Find the diameter of a circle with a circumference of 40.82 inches.

• 12 inches

• 13 inches

• 20.41 inches

• 22 inches

Multiple Choice

7.The circumference is 62.8 inches. What is the radius?

• 20 inches

• 10 inches

• 6.28 inches

• 31.4 inches

Multiple Choice

8.Jayne has a very large circular lollipop that has a circumference of 25.12 inches. What would the diameter of Jayne’s lollipop be? Use π = 3.14.

• 4 in.

• 8 in.

• 12 in.

• 16 in.

Multiple Choice

9.The circumference of a circle is 30π. What is the radius?

• 30

• 60

• 15

• 45

Multiple Choice

10.The circumference of a circle is 12π. What is the diameter?

• 12

• 6

• 24

• 18

Multiple Choice

Serena drew a circle with a circumference of 157 centimeters. What is the approximate diameter of the circle she drew?

• 1.57 cm

• 50 cm

• 15.7 cm

• 25 cm