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ExplorA-Pond:4th Grade Perimeter Estimation

Time Frame:
1 class period that runs 45 minutes.

Group Size:
Small Groups


Students estimate the perimeter of the pond using non-standard and standard units of measure.

Main Curriculum Tie:
Recognize and describe area as a measurable attribute of two-dimensional shapes and calculate area measurements.

Background For Teachers:
In this activity students will be asked to measure the curvilinear perimeter of a pond. An easy way to measure non-linear perimeters is to use string to outline the perimeter. Mark the ending point on the string. In the clasroom pull the string taut and measure the string against a meter or yard stick (a meter is great for introducing students to the concept of tenths, a yard stick for halves, quarters and eighths). You may need to demonstrate converting the length of the string into metric units. If your pond has a large perimeter, you may wish to assign sections of the perimeter to groups and then combine group measurements to find the total perimeter. Visiting a real pond is superior to using a map of the pond. If you use a map of the pond, students must multiply by the scale of the map to convert the perimeter to real world units. Avoid maps that have a scale factor that exceeds the multiplication ability of your students. Many teachers will use masking tape and outline a pond on the floor of their classroom. Students then measure the perimeter of the 'tape' pond and thereby avoid the scaling problems (although scaling objects is part of the fourth grade curriculum).

Intended Learning Outcomes:
Students will measure the perimeter of regions in the environment using non-standard units.

Instructional Procedures:
When people think about pond life many times they will think about fish swimming in the deep areas of the pond. Many other kinds of pond life congregate along the shoreline of the pond. The length of the shoreline is one important factor in determining how much aquatic life lives in the pond. Mathematicians use the word perimeter to describe the length of a pond's shoreline. The challenge for today's activity is to calculate the perimeter of our pond.

1. Visit the pond site (or display an overhead transparency showing a map of the pond). Scan the shoreline for any areas that will create problems for student's measuring the perimeter of the pond (swamps, creeks, holes, etc.).

2. Divide the students into groups of at least three members. Explain that the groups will estimate the perimeter of the pond using non standard units.

3. Assign each group a section of the shoreline and provide string for them to use to measure the perimeter.

4. Encourage the students to keep the string as dry as possible, since some types of string expand when wet. Return to the classroom and convert the length of string to metrics or English common units (inches, feet, yards). See the discussion in the Background section if you are unsure about how to convert the length of string into metric units. Record the length of shoreline measured by each group. Watch for opportunities to draw the students' attention to fractions used in reporting the length of the shoreline.

5. Assign the students to calculate the total perimeter of the pond.

Many states publish the length of their shoreline. Long shorelines are a tourist attraction. Students may wish to compare states with long shorelines with states that are leading tourist destinations. 2. Perimeter is an important concept anytime someone wires a building for new computers. Students could calculate the length of wire needed to run a wire from the door, along the wall and to the teacher's desk (following the perimeter) and compare that to the length required to go up through the ceiling and down to the teacher's desk. 3. Many nations claim a 200 km. swath of seabed as their national domain. You might explore how an additional 200 km wide swath increases the perimeter of your state, nation, or continent.

Assessment Plan:
Students successfully complete the calculations of the perimeter of the pond. Check to see that all students were successful and give remedial help to those who need it.

Created Date :
Mar 19 1999 13:38 PM