Metric Olympics Circles

1
Metric Olympics Circles

• By Scott Mangum

2
Mississippi Framework

• 2c - Use appropriate tools to measure area,
  perimeter, circumference, radius, and diameter in
  the standard (English and metric) systems.

3
Circles
A Circle has all its points equal distance from
the center.
4
Circles

• Vocabulary
• 1. Circle

A
The center is the point in the middle.
Circles are named by their center point.
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Circles

• Vocabulary
• Circle
• Center

The diameter is a chord that passes thought the
center.
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Circles

• Vocabulary
• Circle
• Center
• Diameter

The radius is a segment from the center to any
point on the center.
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Circles

• Vocabulary
• Circle
• Center
• Diameter
• Radius

A chord is a segment that joins two points on a
circle.
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Circles

• Vocabulary
• Circle
• Center
• Diameter
• Radius
• Chord

What is that?
The circumference is the distance around the
circle.
Formula C d
9
What is pi?

• Pi is this big number.
• It is rounded to 3.14
• To find circumference you multiply the diameter
  times 3.14

10
REVIEW
Copy into your booklet page 11

• Vocabulary
• Circle has all its points equal distance from
  the center.
• Center is the point in the middle.
• Diameter (d) is a chord that passes thought the
  center.
• Radius (r) is a segment from the center to any
  point on the center.
• Chord is a segment that joins two points on a
  circle.
• Circumference (C) is the distance around the
  circle.

A
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Practice

• The diameter is 10 inches.
• What is the radius?
• 5 inches

10 inch skillet
12
Practice

• The diameter is 10 inches.
• What is the circumference?
• 31.4 inches

10 inch skillet
13
Practice

• What does the red dot indicate?
• Center

10 inch skillet
X
14
Practice

• What is the name of the circle?
• X

10 inch skillet
X
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Practice

• What does the red line indicate?
• Diameter

10 inch skillet
16
Practice

• What does the orange line indicate?
• Chord

10 inch skillet
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Practice
r 6,378 km

• What is the diameter of the Earth?
• d2r or 2 x 6,378
• d12,756 km