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### Lesson Plan Title : Finding circumference, diameter, and radius

**Age Range:**

Grade 6 through Grade 8 (Middle School)

**Overview and Purpose:**

This activity will allow students to measure the circumference, diameter,
and radius of a circle in a hands-on way. By being able to manipulate a
circle and stretch it out the idea of circumference will be more concrete.
Students will use each other, desks, and chairs to create circles that can
be measured.

**Objective:**

The student will be able to measure a circle to find the circumference,
diameter, and radius.

**Resources:**

Students' desks and chairs

2 different colored balls of string

25 foot tape measure

Math journals

White board and markers

**Activities:**

Discuss the definitions of circumference, diameter, and radius. Write them
on the board and have students copy them into their math journals. Explain
that the students are going to practice measuring circles.

Clear a space in the middle of the room and have several students make
a circle. Pass a ball of string around to the students and cut it when it
gets back to the first student. Explain that this piece of string represents
the circumference.

Line other students across the center of the circle and explain that they
represent the diameter. Pass a different ball of string down this line of
students.

Ask students where the radius is. Explain that the radius is half of the
diameter. Show them that you can accurately find the radius by folding the
diameter string in half.

Have the students stretch the circumference string out and measure it and
the diameter one. Have them divide the diameter in half to get the radius.

Repeat this exercise several times with different size circles and using
different items. If students are using their desks they can wrap the string
around the outside of their desks to hold it in the shape of a circle. Students
will enjoy coming up with unique ways to make the circles and finding items
they can use to represent diameter.

**Closure:**

This lesson is a great lead in to teaching the formulas students will need
to memorize to measure circumference, diameter, and radius of circles. A
smaller version of this lesson can be used as homework or in a math center
with short pieces of string, rulers, and teacher created worksheets.