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ExplorA-Pond:2nd Grade Perimeter

Time Frame:
2 class periods that run 45 minutes each.

Group Size:
Small Groups



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

If you are unable to visit a real pond then you may use masking tape to outline a pond on the floor of your classroom or use a printout of the virtual pond.

Background For Teachers:
It is assumed that students can add two digit numbers with regrouping at this point. It is also assumed that students have been introduced to the concept of perimeter (distance along the boundary of the object). If you wish to refer to the perimeter of the pond as 'shoreline' that would be acceptable in this lesson, but be sure to mention that every object has a perimeter, while only bodies of water have shorelines.

The unit of measure for this activity will be the student's foot. Students will be asked to measure the distance by placing one foot ahead of the other (heel of forward foot against toe of rear foot) and counting the total number of student feet around the pond. This measuring technique requires coordination and may require some practice on dry land before moving to a real shoreline.

This activity works best if students can measure the shoreline of a real pond. Using a map adds the additional concept of 'scale'. changing from map measurements to real world measurements requires multiplying by the scale of the map and is beyond the mathematical background of most second graders. Some teachers will create a 'tape pond' on their classroom floor that is similar to the virtual pond. Students can then estimate the perimeter of the masking tape pond on the floor and avoid the problems of scale.

Intended Learning Outcomes:
Students will estimate the perimeter of a region in the environment using non standard units. Students will make and use estimates of measurement.

Instructional Procedures:
Point out that while fish enjoy the center of a pond, much pond life can be found near the shore. The type of soil along the shore has a big impact on the type of life found in a pond. The length of the shoreline is another important factor in how much aquatic life a pond will support. Mathematicians use a special word when they talk about the length of an object's boundary. Perimeter is the word used by mathematicians to describe the length of the boundary of an object. Review new vocabulary words like: perimeter, shoreline, meter stick, and yard stick. 1. Visit the pond site. Scan the shoreline for any problems that will interfere with the measurement of the shoreline (swamps, holes, creeks, etc.) 2. Assign each group a section of shoreline to measure. Collect the estimates (using units of student feet) as described in the background section above. 3. In the classroom write the group measurements on the board and ask the students to find the total shoreline in 'student feet'. this will give them a chance to work on their addition skills. 4. Point out that the size of a foot changes as a child grows up. To avoid changing feet sizes, mathematicians have agreed to use a meter stick as the standard for making measurements when they share results with others. 5. Ask a volunteer to come to the front of the classroom where his/her foot can be traced onto a piece of paper. Measure the length of the foot in standard units (centimeters if you wish to avoid fractions). 6. Demonstrate how to convert the 'student feet' estimate into standard units using repeated addition (if you have a calculator that projects to the class, the SUM key can be quite helpful here). Teacher Note: Using repeated addition helps avoid multiplication here. The Pond's shoreline will likely exceed the two digit amount if centimeters are used, so you may need to total the perimeter for the students. To convert the total perimeter from centimeters to meters, divide the number of centimeters by one hundred.

1. You may wish to compare the meter stick to the yard stick. 2. Long lengths of butcher paper could be used to trace the outline of one group member. The remaining group members could measure the student's perimeter in 'student feet'. 3. It is interesting to compare the length of the students in metrics and common English units (feet and inches).

Created Date :
Mar 19 1999 13:38 PM