# Stage 4 -measurement – perimeter and area – polygons

## Strategy

Students can:

• use formulae to calculate area and perimeter
• calculate the area of composite shapes

## Activities to support the strategy

1. Students brainstorm when people might need to calculate the area and perimeter of different objects and why this is important, e.g. for buying carpet for houses, tilers working out the number of tiles to order for a job, builders when building houses.

Students measure the area and perimeter of objects in their surroundings, such as desks, classrooms, the oval or the playground. Discuss which measuring tool is the best to use to measure different areas and objects, for example, a trundle wheel for measuring larger areas, a ruler or tape measure for measuring tables.

Investigate the relationship between:

• length, width and area. Students use the formula to calculate area.
• length, width and perimeter. Students use the formula to calculate perimeter

2. Students use a fixed number of square centimetres to make different shapes. Students:

• calculate the perimeter of each shape
• calculate the area of the same shapes

Students investigate the area and perimeter of these shapes by answering questions such as:

• Can we remove any squares and keep the perimeter the same? Why?
• Can we remove any squares and keep the area the same? Why?
• Can we move any squares and keep the perimeter the same? Why?

3. Work through examples of calculating area of composite shapes by dividing them into 2 or more common shapes, such as rectangles, triangles and squares.

View/print 'Calculating area of composite shapes' template (PDF 285.52KB)

## References

### Australian curriculum

ACMMG196: Find perimeters and areas of parallelograms, trapeziums, rhombuses and kites

### NSW syllabus

MA4-12MG: Calculates the perimeters of plane shapes and the circumferences of circles.

MA4-13MG: Uses formulas to calculate the areas of quadrilaterals and circles, and converts between units of area.

## Teacher resources

Teaching the full range of students in your class a unit of work on area. Students can develop formulae for the area of squares, rectangles, triangles and parallelograms. The key features of this unit are assessment for learning, a unit overview, flexible teaching approaches focusing on concept development and flexible student grouping.

Numeracy wraps

• Round the outside - students can calculate the perimeter of different shapes, choose the appropriate measuring device and make different shapes from given perimeters.

### Lesson plans and activities

• Webquest – Using area and perimeter to design a Fun House