Year 9 Mathematics – Term 2 (WA Curriculum): Measurement and Geometry - Triangles, Circles, and 3D Objects

What this unit covers

In Term 2, Year 9 Mathematics in the WA Curriculum centres on the unit “Measurement and Geometry - Triangles, Circles, and 3D Objects”.

Students explore perimeter and area calculations for triangles, quadrilaterals and circles, investigate triangle properties including congruence and similarity, apply trigonometry in right-angled triangles, calculate volumes and surface areas of cylinders and prisms, and solve real-world problems using scale drawings and geometric transformations.

Lesson sequence (30 lessons)

The unit breaks down into the following lesson-by-lesson sequence — each title below is a teachable lesson, in order:

1. Calculating perimeters of triangles using direct measurement
2. Finding perimeters of quadrilaterals and irregular shapes
3. Exploring circumference of circles and sectors
4. Using Pythagoras' theorem to find perimeters
5. Applying symmetry and transformations to determine perimeters
6. Estimating and approximating perimeters of complex shapes
7. Testing triangles to determine if they are right-angled
8. Calculating height, area and perimeter of right-angled triangles in exact form
9. Converting exact measurements to approximate decimal values
10. Solving problems with right-angled triangles using given dimensions
11. Constructing triangles with three given sides
12. Building triangles using two sides and an included angle
13. Identifying corresponding sides and angles in congruent triangles
14. Explaining reasoning for triangle congruence using dynamic geometry
15. Proving triangle congruence in different orientations
16. Creating similar figures through enlargement techniques
17. Constructing similar figures using reduction methods
18. Using grids and centres of enlargement to create similar shapes
19. Establishing properties of similar figures through construction
20. Applying similarity properties to solve geometric problems
21. Identifying hypotenuse, adjacent and opposite sides in right triangles
22. Understanding sine, cosine and tangent ratios
23. Using trigonometric ratios to find unknown side lengths
24. Applying trigonometry to find unknown angles in right triangles
25. Verifying trigonometric ratios using similar triangles
26. Interpreting maps, plans and scale drawings
27. Determining scales between drawings and actual measurements
28. Using scale factors to calculate real-world dimensions
29. Solving problems involving floor plans and architectural drawings
30. Applying proportional reasoning to photographs and maps

Curriculum codes in this unit

Content codes:

Reading the codes: WA codes (the ones starting with WA) pack the year level, learning area, strand and content number into one string, while the national Australian Curriculum v9 uses a different anatomy that starts with AC9 — same content family, different labels. Our complete WA Curriculum guide decodes both, character by character.

Planning notes for Term 2

WA terms run roughly 9–11 weeks, and in 2026 Term 2 runs from Monday 20 April to Friday 3 July — 11 weeks for WA public schools. With 30 lessons in this unit, that leaves breathing room for assessment, moderation and the weeks that disappear to carnivals, camps and public holidays — plan the assessable work to land two to three weeks before the end of term rather than in the final week.