Circles Circumference and Area

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CirclesCircumference and Area

• 6th Grade Math
• LaVergne Middle School

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Circles (terminology)

• Radius- The distance from the center of a circle
  to the edge.

3
Circles (terminology)

• Diameter- The distance across a circle, through
  the center.

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Radius vs. Diameter

• The radius is ½ the diameter.
• The diameter is 2r.

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Pi

• Pi is a Greek letter which is written as p. Pi
  written as a decimal value is 3.14 or as an
  improper fraction is 22/7. Pi is an
  approximation.

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Circumference

• The circumference of a circle is the distance
  around a circle.
• Formula C pd
• C 2pr

4 in.
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Area of a Circle

• The area of a circle is the number of square
  units needed to cover the inside of a circle.
  (Think of a blanket)
• Formula A pr2

7 cm.
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Find the circumference and area.
D 24 cm
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Find the circumference and area.
R 0.75 in
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Find the circumference and area.
D 78 cm
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The radius is shown in the circle below. Find
the area and circumference.
R 52 cm
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Find the circumference and area.
D 4.5 cm
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Ticket Out!

• Which measurement is closest to the
  circumference of a circle with a radius of 3 cm?
• 9.42 cm
• 18.84 cm
• 28.26 cm
• 138.16 cm