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# reSolve: Mechanical Linkages: Similar Triangles

This sequence of lessons explores the geometry of similar triangles using two real-world objects: ironing boards and pantographs. In the first lesson, students investigate different ironing board leg lengths and pivot positions using similar and congruent triangles. In the second lesson, they use their knowledge of parallelogram properties and similar triangles to explore and explain how pantographs work. Each lesson is outlined in detail including curriculum links, materials needed, sample answers, discussion points and student resources such as links for simulations online. This sequence is part of the reSolve: Maths by Inquiry special topic 'Mechanical linkages and deductive geometry'.

Year level(s) Year 9
Audience Teacher
Purpose Teaching resource
Teaching strategies and pedagogical approaches Mathematics investigation
Keywords triangles (shapes), dilation, similarity (geometry), explicit teaching

## Curriculum alignment

Curriculum connections Numeracy
Strand and focus Space, Build understanding, Apply understanding
Topics Angles and geometric reasoning
AC: Mathematics (V9.0) content descriptions
AC9M9M03

Solve spatial problems, applying angle properties, scale, similarity, Pythagoras' theorem and trigonometry in right-angled triangles

Numeracy progression Understanding geometric properties (P7)
Understanding units of measurement (P10)
Proportional thinking (P7)