## Square Circles

### Carol SpiceSanta Rosa District Schools

#### Description

Show your students how a circle can be measured in square units and how diameter, radius, and circumference are related.

#### Objectives

The student solves and explains problems involving perimeter, area, and circumference.

#### Materials

- Grid paper (you can use any size but I find .5 cm. works well)
- A compass
- Each student needs a pencil
- Formulas for circumference and area of a circle. (I give each student a copy of the FCAT reference sheet at the beginning of the year to keep in his/her folder to use all year)

#### Preparations

1. On the front and back of the grid paper, draw 5 different size circles. Draw a dot in the center of each circle.
2. Copy, cut, and paste the following to the right of each circle.
r = ____________

d = ____________

C = ___________

A = ___________

3. Copy one grid paper with circles and blanks for each student.

#### Procedures

1. Pass out grid paper with pre-drawn circles.

2. Instruct the students to find the diameter and radius of the first circle by counting the blocks and then to write the results in the spaces provided. Circulate and assist as needed.

3. When each student has found the diameter and radius, discuss how the students could find out the approximate area and circumference by using the same procedure. Explain that formulas provide us with an easier way to determine area and circumference.

4. Show the students how use the formulas to find the circumference and area by working the problems for the first circle out on the overhead.

5. Instruct students to calculate the diameter, radius, circumference, and area of the rest of the circles. Circulate and assist.

6. Collect the grid papers.

#### Assessments

NOTE: This lesson doesn not address perimeter.
1. Students will be informally evaluated by teacher observation.
2. Assess papers. Students score high on this because as I am circulating I can quickly see if a student does not understand and give the student further assistance.