Perimeter (Lesson 1) Mathematics Strand: Measurement

FOCUS QUESTION

How do I calculate and use the various measurements around me?

SPECIFIC OBJS.

1. Calculate the perimeter of regular and irregular polygons.

2. Calculate the measurement of one side of a polygon given the perimeter and the lengths of the other sides

CONTENT SUMMARY

Perimeter is the distance around a shape.

Polygons are multisided shapes. All polygons have sides, vertices and angles. Poly means many. They are closed shapes. Polygons are two dimensional or flat shapes. This means they must lie on the same plane.

A polygon is considered a regular polygon if it has equal sides and equal angles. On the other hand, irregular polygons do not have equal sides or equal angles.

ENGAGE

Pupils will watch a youtube video clip (Math Antics- perimeter) to review the topic for the day. (Perimeter). Formulate a working definition for ‘perimeter’.

EXPLORE

Students will watch youtube video clip (MathsAntics-Polygons) to glean information on polygons and the properties of polygons. They will name some of the polygons they are familiar with. Tell the difference between regular and irregular polygons.

Now let us identify the ones that are regular and the ones that are not.

Other video clip

EXPLAIN

Tell what polygons are and the properties of every polygon. In sentences, tell the difference between regular and irregular polygons

EXTEND/ELABORATE

Examine the polygons projected on chalkboard. They will classify them as regular and irregular, based on their measurements.

Students I want you to read the problems below and try to decide on the answers. Be ready to explain how you arrived at the answers.

Eg,

1. The perimeter of a regular nonagon is 81 cm. Find the length of one of its side.

2. The sides of an irregular polygon are 5cm, 6cm, 4cm, 8cm and x cm. If the perimeter is 29cm, what is the length of the missing side x?

Measure the lengths of polygons given by teacher and those taken by students. They will classify them as regular or irregular, and find their perimeter.

EVALUATE

TASK 1

TASK 2

TASK 3

(a) A regular nonagon has a perimeter of 88cm. Find the lengths of one of its sides.

(b)i 4 sides of a polygon are 6cm, 9cm, 17cm, 4cm and x cm. What is the measurement of the side x?

ii What is the name for this polygon?

TASK 2

FOLLOW UP PRACTICE EXERCISES

Lesson Plan – Mathematics (Grade 6)

Topic: Finding Perimeter
Duration: 1 hour
Focus Question: How do I calculate and use the various measurements around me?

Objectives

By the end of the lesson, students should be able to:

Calculate the perimeter of regular and irregular polygons.
Determine the measurement of one side of a polygon given the perimeter and the lengths of the other sides.

Materials

Rulers, measuring tapes
Chart paper & markers
Printed diagrams of regular & irregular polygons
Real-world objects to measure (e.g., tabletops, windows, books)
Calculators
STEM activity cards

5E Lesson Stages

1. Engage (5 minutes)

Hook: Show students two photos:
- A fenced rectangular garden.
- An irregular-shaped park.
  Ask: “If you were building a fence around these, how would you figure out how much material you’d need?”
Allow quick responses, then introduce the term perimeter.

2. Explore (10 minutes)

Activity:
- In pairs, students use rulers/measuring tapes to measure objects around the classroom (e.g., desks, doors, whiteboard).
- They record measurements and add up all sides to find the perimeters.
- Introduce both regular polygons (all sides equal) and irregular polygons (sides of different lengths).
STEM Connection: Link to engineering — "Engineers calculate perimeters when designing buildings, playgrounds, and road layouts to know material requirements."

3. Explain (15 minutes)

Teacher explains:
- Perimeter Formula for Regular Polygons:
  $P = \text{Number of sides} \times \text{Length of one side}$
- Perimeter of Irregular Polygons: Add the lengths of all sides.
- Finding an unknown side:
  $\text{Missing side} = P - (\text{sum of known sides})$
Example Problems:
1. Find the perimeter of a square with each side 5 m.
2. Find the perimeter of a pentagon with sides 7 cm, 8 cm, 6 cm, 7 cm, 9 cm.
3. A rectangle has a perimeter of 50 m. Three sides measure 15 m, 10 m, and 15 m. Find the missing side.

4. Elaborate (20 minutes)

Hands-On STEM Project:
- Students receive floor plans of a small classroom, garden, or sports field (with given or missing measurements).
- Task 1: Calculate total perimeter for fencing or edging.
- Task 2: If one side is missing, calculate its length.
- Extension: Discuss how calculating perimeter helps in budgeting materials and reducing waste in construction.
Differentiated Learning:
- Tier 1 (Support): Work with regular shapes and small whole numbers.
- Tier 2 (On-level): Work with irregular polygons and mixed units.
- Tier 3 (Challenge): Solve multi-step word problems involving unit conversions and missing sides.

5. Evaluate (10 minutes)

Three-Tier Evaluation:
- Level 1 (Basic): Find the perimeter of a square with each side 6 cm.
- Level 2 (Proficient): Find the perimeter of an irregular pentagon with sides 5 cm, 7 cm, 6 cm, 8 cm, 7 cm.
- Level 3 (Advanced): A triangle has a perimeter of 42 m. Two sides measure 15 m and 14 m. Find the length of the third side.
Assessment Method:
- Check for accuracy of calculations.
- Observe reasoning when explaining answers.

Homework

Measure three objects at home, draw them, and calculate their perimeters. Identify if they are regular or irregular shapes.

GRADE 6 CONCEPTS - (NSC) by Janice Bowes-Wellington

Friday, October 30, 2020