The Awesome Figures of Circles

1
The Awesome Figures of Circles

• Screen Bean Says, Circles Are Awesome Figures in
  Our World!

Circle, Diameter, Radius, Circumference,
Pi Presentation by Bobbie J. Taylor 2009
2
Objectives Understanding Some Measurements of
Circles
What are the measurements inside, around, and
across a circular swimming pool?

• Circle
• Diameter
• Radius
• Circumference
• Area
• Pi
• Practice Makes Perfect

3
WHAT IS A CIRCLE?
The kids say, Screen Bean first needs to know
the definition of a circle.
A circle is a closed flat figure in which every
point is the same distance from a given point,
called the center of a circle.
4
Diameter and Radius
Next, Screen Bean, you should know the diameter
and radius of a circular pool.
A
5 m
10m

• Diameter
• Diameter describes both
• a line segment through
• the center of a circle with
• endpoints on the circle
• and the length of that
• line segment. The diameter of a circle is always
  2r.

• Radius
• Radius is any segment that
• has one endpoint at the
• center of the circle and the
• other endpoint
• on the circle. The radius is always ½d.

5
Circumference and Area
Wait, Screen Bean, you need to know the
definition and formula for circumference and area
of a circle before you swim across the pool.

• Circumference is the distance around a circle.
• Area is the distance within a circle.
• The formula for a circumference of a circle is
  pd or 2pr.
• The formula for area of a circle pr2.
• Pi is approximately 3.142

6
Pi

• Pi
• Pi comes from the Greek letter pi which is
  written as p.
• Written as a decimal, pi is close to the decimal
  approximation, 3.141592653589793

7
Practice Makes PerfectProblem Solving and
Critical Thinking

• What is the correct term for the distance across
  a circular swimming pool?
• If Screen Bean wanted to know half the diameter
  of a circular swimming pool, what term is need?
• Circumference measures what around a circular
  pool?
• What formula can be used to find the area of a
  circle?

• A swimming pool has a diameter of 100 m. What is
  its radius?
• If a radius of a swimming pool is 30 ft, what is
  its diameter?

8

• Summary

Screen Bean says, I have learned some basic
measurements of a circle, and Im now ready to
swim the distance across the pool. Screen Bean
also thanks his teachers for explaining to him
some geometric terms for circles and the awesome
role circles play in our world.