## Wrap it Right!

### Delia PogorzelskiLeon County Schools

#### Description

Are you tired of miscalculating the length of ribbon needed for a gift? No more cutting & re-cutting for you. This lesson teaches how to eliminate this frustration. It's a failsafe method, and it's just in time for any gift-giving occasion!

#### Objectives

The student uses concrete and graphic models to create formulas for finding the perimeter and area of plane figures and the volume of rectangular solids.

#### Materials

-Assortment of rectangular or square boxes differing in shapes and sizes
-One spool of ribbon
-One skein of yarn
-Measuring tools: rulers, one per student; measuring tape, one for teacher use
-One roll of transparent tape
-One pair of scissors
-Glue stick, one per student
-One piece of paper for each student
-One writing utensil for each student

#### Preparations

1. Gather supplies.
2. Implement lesson.

#### Procedures

Note: This lesson uses graphic models for finding perimeter and for creating formulas relating to perimeter. Area will not be addressed but could be demonstrated as an extension in another lesson.

1. As students enter the classroom attempt to tape a piece of ribbon around one box. Make certain that the ribbon you are using is too short to fit. Continue this process until your students suggest that you cut a very long piece of ribbon.

2. Explain to your students that the ribbon you are using was very expensive and you do not want to continue wasting it!

3. State that you wished there was a process, which would help calculate the measurement accurately.

5. Choose one box to work with and as a class trouble shoot. Have students tell you what they know about this particular box. For example, they can measure the length and width of this box.

6. Next, wrap the ribbon around the box but do not tape the ribbon to the box. Once you have determined the amount of ribbon needed to border this box, cut it. Then, place the ribbon on a flat surface. Measure the ribbon.

7. Give students who need additional practice their own boxes and ribbon, and have them repeat this process.

8. Have students draw several geometric figures on a piece of paper. Next, have the students measure each side. Finally, have students calculate the perimeter of these figures by adding the measurements of each of the sides (thereby creating a formula). A student might show that he or she is adding the four sides of a square to calculate the perimeter; (s + s + s + s = P), or he or she may say that he or she doubled the length and doubled the width, then took the sum; (2l + 2w = P)

9. Give students a piece of yarn. Using the determined perimeter calculated on #8 above, have students measure and cut the ribbon the length of this perimeter. Have students check the measurement of the yarn to confirm its length equals the perimeter. Then, glue the yarn to the sides of the figures, which were drawn on the paper by the students.

10. Observe and discuss these processes as students measure and cut the yarn. For example, How much yarn is needed to surround the shape?, How did you determine this amount?, What might have happened if the yarn is too short and doesn't surround the shape?

11. Ask the students if this process will always work? If not, site examples (hat-boxes, round gift boxes).

12. Discuss extensions for this process (wall-paper, fences).

13. Ask students to suggest occupations, which may need to use perimeter (gift wrapper, surveyor, wall-paper hanger, gardener).

#### Assessments

Students submit geometric shapes drawn and surrounded with yarn. The student's shapes include the measurement of each side, and the units. Students include the formula used to calculate the perimeter. (For example: A picture of a pentagon is drawn. Labeling includes dimensions and units for each side. Formula for calculating the perimeter is shown, i.e., 5 inches + 4 inches + 6 inches + 2 inches + 1 inch = 18 inches). Formatively assess students' accuracy in 4 areas (drawing, labeling, formula, and calculation).