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Geometry
Circles
in Geometry
Overview: Grade
school geometry doesn't have to get into a detailed lesson on Pi to communicate
the basics of this constant.
Teacher Preparation: flexible tape measure.
Procedure Ideas:
 Break into groups,
giving each group something circular to measure, both the diameter and
the circumference. Then divide the circumference by the diameter to
get a number. When all groups are finished, have each group read off
the answer to the division problem. Use this as a leadin to your further
discussion of circle properties.
 Ideas of circular
items to measure: basketballs, softballs, globes, hoolahoops.
 A wholeclass activity
could be: have one student stand in the middle of the gymnasium, holding
one end of a known length of string. Then walk the other end of the
string around to form a circle, placing students evenly on the imaginary
circumference. When finished, you should have your students representing
a fairly good circle, with one in the middle. Use the tape measure to
find the diameter, using the center student for accuracy in measuring
through the circle's center. Then measure the circumference as well.
Calculate for Pi.
 Discuss realworld
applications for knowing Pi to estimate circumferences of objects
or areas: How long a piece of paper must be to cover a round container
for an art project; finding the actual diameter of the earth by using
a globe with a distance scale to first determine the circumference.
 For everything
you wanted to know (or didn't want to know) about Pi, there
is a Yahoo site.
 Assign students
to work with their parents in finding uses for estimating circle circumferences
at home. Starting points might be length of a circular sidewalk around
a flower bed, how much paint needed to cover a round structure, how
long a piece of wire is needed to make a round perch for a bird feeder.

