Geometric measurement: recognize perimeter as an attribute of plane figures and distinguish between linear and area measures.
3.MD.8 Solve real world and mathematical problems involving perimeters of polygons, including finding the perimeter given the side lengths, finding an unknown side length, and exhibiting rectangles with the same perimeter and different areas or with the same area and different perimeters. / Emphasized Standards for Mathematical Practice:4. Model with mathematics
5. Use appropriate tools strategically.
6. Attend to precision.
Materials:
Copies of Mystery Perimeter Warm-Up (1 per pair of students) / Words that you should hear students using in mathematical conversations:
sides
triangle, quadrilateral, pentagon, hexagon, octagon,
sum perimeter length
Ten Minute Math:
Go to www.discoveryeducation.com and log in (ALL CMS teachers have a discovery education log-in. See your math/literacy facilitator if you have trouble). Click the following link http://app.discoveryeducation.com/player/view/assetGuid/E3755740-277A-4B96-BD61-3F58CA647274 (click “introduction” video). This video shows perimeter as a fence and references the shape. After watching the video, ask students “Do you have to measure every side of a rectangle to find the perimeter?” Turn and talk with a partner. Ask for a few student responses. Finally, click the NEXT arrow on the video to play the video “Warm Up”. This video shows why it’s not necessary to measure all sides of a rectangle. Ask students, “Can you think of another shape where you wouldn’t need to measure all of the sides to find the perimeter?”
Before:
http://app.discoveryeducation.com/player/view/assetGuid/E3755740-277A-4B96-BD61-3F58CA647274
Click video “Rectangles and Perimeter” this video shows an irregular shape and gives students a strategy for finding unknown side lengths. Click the NEXT arrow to show the FIRST 15 SECONDS ONLY of the video “The Test”.
Give each pair of students the Mystery Perimeter Warm-Up (this is the same perimeter that is shown on the video “The Test”. Tell students you are going to give them some time to determine the missing side lengths and the perimeter of the shape. Remind students they may use tools that will help them (graph paper, square tiles, centimeter cubes, or any other appropriate math tool).
During:
Give students about 15-20 minutes to complete this task. If students struggle, suggest they re-create the shape using a math tool and/or divide the shape into rectangles.
Once most students have gotten a good start on the task, interrupt them to ask several students to share their strategy by asking, “How are you starting to solve this task?” The focus here is on entry strategies, not the answer.
If students finish early, ask them to create a mystery perimeter for their partner to solve. They may use paper or another math tool.
After:
Ask students to share how they determined the missing lengths in the shapes.
Then have them share how they determined the perimeter of the entire shape. Be sure to have students who share write their equations on the board for all students to discuss.
Evaluation:
Teachers choice based on student needs.
MYSTERY PERIMETER WARM-UP
MYSTERY PERIMETER WARM-UP