Spanish Math 35
Bulletin Board Border
Please help me. I would like to make a geometry bulletin board that has a border of circles, triangles and squares. I know that 20 shapes will fit across the board and that 12 shapes will fit down the board. If I start in the top left hand corner with a circle followed by a triangle then a square and repeat this pattern all around the board, how many of each shape will I need?
Explain your solution using words and pictures.
Suggested Grade Span
Grades 3–5
Alternative Versions of Task
More Accessible Version:
Please help me. I would like to make a geometry boarder on the wall across my classroom. I would like to use a pattern of circles, triangles and squares. I know that 21 shapes will fit across the wall. If I start with a circle, followed by a triangle, then a square and repeat this pattern, how many of each shape will I need? Explain your solution using words and pictures.
More Challenging Version:
Please help me. I would like to make a geometry bulletin board that is surrounded by a border of polygons. I will start in the top lefthand corner with a 4sided shape, followed by a 5sided shape, then a 6sided and so on all the way up to a 10sided shape. Once I get to a 10sided shape I will start the pattern again with a 4sided shape. I know that 20 shapes will fit across the board, and that 12 shapes will fit down the board. How many of each shape will I need to surround the bulletin board? Explain your solution using words and pictures.
Context
This problem worked well because it allows students to diagram the problem and show all their work. Students first thought they could add all the numbers given and solve the problem without a diagram. When they became involved in the problem solving they realized why drawing clear diagrams is so useful.
What This Task Accomplishes
This task allows students to explore a reallife problem using perimeter. It assesses their ability to take information given and apply it to a diagram.
What Students Will Do
The task provides information that most students will need to diagram. Some students in my fourthgrade class had difficulty placing the corner pieces and counted them twice. The more accurate the diagram, the more accurate the solution.
Time Required for Task
Approximately 60 minutes
Interdisciplinary Links
None, this is strictly a problemsolving task.
Teaching Tips
Teachers tell students that a diagram will help them with problem solving, but we often get, “I did it in my head.” This problem allows students to draw a simple diagram to a challenging problem. It allows students the opportunity to actually make the border on a bulletin board.
NCTM Standards
 Numbers and Operations
 Geometry and Measurement
Concepts to be Assessed and Skills to be Developed
 Problem solving
 Reasoning
 Communication
 Patterns
 Perimeter
Suggested Materials
 Paper
 Pencil
 Actual shapes may be used
Possible Solutions
Original Version:
Students may conclude that 64 shapes are needed. They will add the numbers given in the task and draw a diagram that represents their interpretation. Hopefully by drawing a diagram, students will use the corner pieces correctly, and conclude that 60 shapes are needed, 20 of each shape.
More Accessible Version:
21 ÷ 3 shapes = 7 of each shape
More Challenging Version:
20 + 20 + 10 + 10= 60 shapes around board ÷ 7 different polygons = 8 polygons with 4 shapes having an extra one:
Quadrilaterals = 9
Trapezoids = 9
Hexagon = 9
Septagon = 9
Octagon = 9
Nonagon = 9
Decagon = 8
TaskSpecific Assessment Notes
Task Specific Rubric/Benchmark Descriptors Click on a level for student example. 


Novice  The Novice will use inappropriate concepts and procedures to solve the problem (s/ he may have multiplied 20 by 12 to get 240). There will use little evidence in the explanation of a strategy or reasoning. The diagram will not relate to the problem (there will be no evidence of a border). 
Apprentice  The Apprentice will understand part of the problem and will show some mathematical reasoning, (using a pattern of shapes for the border) but will not use the corner pieces as a continuation of the pattern. There will be some use of a diagram and mathematical notation. 
Practitioner  The Practitioner will have an understanding of the problem and a strategy will be used that successfully solves all parts of the task. The student will use an accurate pattern of geometric shapes in the corners and a connection, observation or verification of the solution will be made. 
Expert  The Expert will have a clear understanding of the problem and all of the parameters. The pattern of geometric shapes will continue around the corners. Accurate mathematical representation will be shown, and mathematical reasoning will reflect refined reasoning skills. A connection, observation or verification of the solution will be made. 
Novice
Apprentice
Practitioner
Expert