# PICKET FENCE AROUND THE GARDEN

by: Lydia Treviño
Lantrip Elementary School
East District
Houston I.S.D., Texas

Subject: Math

### TOPIC:

Geometry-Measurements: Perimeter & Area (Visualization/Spatial)

#### Purpose:

Students will.....
• Make different shaped plots and consider the perimeters, area and shapes.
• Compare shapes with same area.
• Discover that shapes with same area can have different perimeters.

#### Materials:

• 6 Cuisenaire rods per pair of students
• 2 whites
• 2 reds
• 2 light greens
• 1 centimeter grid paper - several sheets per pair
• 1 centimeter gird paper transparency (optional)

#### Prior Knowledge:

Concept of geometric shapes and metric unit measurements
Cuisenaire Rod values
• White = 1 centimeter
• Red = 2 centimeter
• Light green = 5 centimeters

#### Time:

45 minutes to an hour

## Procedures:

### Teacher models:

1. Have students arrange 3 rods (2 reds & a light green) on grid so that the rods lie within the grid lines and at least one centimeter or each touches another. Trace around the shape.
2. Remove the rods and show the class your "plot". have the students confirm the area of the plot (have them count each unit used on the grid paper). The part covered with the Cuisenaire rods would be the part covered by grass - this is the area that would be the garden.
3. Ask the students to figure out how long a fence would be needed to fence in the grass. Have the students count the sides of of the rods that face the outside of the plot - remember that each unit should equal to 1 centimeter.
4. Reinforce the difference of what is perimeter and what is area by again emphasising. Ask student to count the units with you and ask questions such as:
• "How many units make up the perimeter of the plot?"
• "The perimeters equals ____ cm.?"

### Next:

1. Have the students draw a 3 cm by 9 cm rectangle and a 6 cm by 6 cm square on the centimeter grid paper and find the perimeter of the rectangle and the square.
2. Have the students compare the number of units in each figure. Ask: "How can two figures with the same perimeter contain a diferent number of unit squares?" (The answer should be:The perimeter is the distance around a figure, not the space inside it.)

### ON THEIR OWN:

Students work in pairs......
Use Cuisenaire rods:
• 2 whites
• 2 reds
• 2 light greens
Use all 6 rods to create a plot - Place rods on grid paper so they lie within the lines of the grid and all rods touch. (each grid square = 1 cm).
1. Students will draw each shape created and find the perimeter and the area of each shape plotted.
2. Use the same 6 rods to create other plots. Each plot should have a different shape. Record each plot and find its perimeter and area.
3. Each pair of students can discuss what was noticed about the area and perimeters of each plot built.
These pages were developed through GirlTECH, a teacher training sponsored by the Center for Research on Parallel Computation (CRPC),a National Science Foundation Science and Technology Center.