Close message Scootle has stopped supporting resources that use the Adobe Flash plug-in from 18 Dec 2020. Learning paths that include these resources will have alerts to notify teachers and students that one or more of the resources will be unavailable. Click here for more info.

Mathematics / Year 9 / Measurement and Geometry / Geometric reasoning

View on Australian Curriculum website Australian Curriculum, Assessment and Reporting Authority
Curriculum content descriptions

Use the enlargement transformation to explain similarity and develop the conditions for triangles to be similar (ACMMG220)

Elaborations
  • establishing the conditions for similarity of two triangles and comparing this to the conditions for congruence
  • using the properties of similarity and ratio, and correct mathematical notation and language, to solve problems involving enlargement (for example, scale diagrams)
  • using the enlargement transformation to establish similarity, understanding that similarity and congruence help describe relationships between geometrical shapes and are important elements of reasoning and proof
General capabilities
  • Literacy Literacy
  • Numeracy Numeracy
ScOT terms

Dilation,  Triangles (Shapes),  Similarity (Geometry)

Refine by learning area

Refine by topic

Related topic * No suggestions
Online

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 ...

Text

Volume of a Pyramid and a Cone

This resource is a web page containing an investigative task to explore volume. Derive the formulae for the volumes of a square-based pyramid and a cone, using mathematical concepts. A printable resource is also available to support the task. This resource is an activity from the NRICH website.

Text

Indigo Interior

This resource is a web page containing a problem solving task that requires an understanding of Pythagoras' theorem. The task involves finding the area of shaded region with a circle with a known area. To solve the problem students need to establish a right angled triangle and apply Pythagoras' theorem. A printable resource ...

Video

Mapping the sea floor

Hydrographers chart the seabed and coastline, giving ships a map to help them avoid running into underwater trouble. Use this clip as a context for exploring the mapping of the sea floor. Think about scale and how to indicate different depths using contour lines.

Video

Mystery man Pythagoras meets his match

What do you know about Pythagoras? Join Vi Hart as she not only explains his theorem but raises some legends about his dark past! Follow Vi's timeline of famous mathematicians to find out in which century Pythagoras lived. See how Vi shows a proof of his theorem and raises what was a big dilemma for Pythagoras: the irrational ...

Online

reSolve: Gradient and Tangent

This sequence of two lessons investigates gradient and angle by applying the tangent ratio to find the angles represented by a road sign or the angle of a street. In the first lesson, students research what a road grade is and determine the actual angle of a road given its grade. They then construct their own road sign ...

Online

reSolve: Pythagoras' Theorem - Lunch Lap

In this sequence of two lessons, students apply Pythagoras' Theorem to explore a practical problem involving optimising paths to lunch carts. In the first lesson, students investigate the length of a path that touches three sides of a rectangle, starting and finishing at the same point. They model the problem, use Pythagoras' ...

Image

'Fishing for upokororo', 1922

This is a black-and-white photograph of two Mäori men at work with two hïnaki (fish traps) capturing upokororo (grayling, 'Prototroctes oxyrhynchus') on the Waipu River on the east coast of the North Island in 1922. The photograph shows a low dam that has been built across the stream to divert its flow and direct the fish ...

Online

reSolve: Mechanical Linkages: Geometry Proofs

This series of six lessons explores geometry proofs using real world contexts focused on the dynamics of linkages and moving joints. Students use physical models and computer simulations, the lessons move from a view of geometry as a study to static diagrams to encompass movement. Each lesson is outlined in detail including ...

Online

reSolve: Tree Biomass

In this sequence of two lessons, students investigate how many trees would be required to supply paper for their school for a year. Students use similar triangles, Pythagoras' Theorem and algebra to design and construct a Biltmore stick, used to measure the diameter and height of a tree. They measure trees, calculate their ...

Online

reSolve: Quarter Cartons

This lesson challenges students to use algebra and proportional reasoning to investigate how changing the size of a paper square or rectangle impacts the dimensions of a box folded from that paper. Students apply knowledge about nets of 3D objects and explore algebraic relationships through a set of hands-on activities ...

Online

reSolve: Algebra: Triangle Inequality

This sequence of two lessons explores the triangle inequality theorem. Students are challenged to construct triangles with a given number of matchsticks, explore and record what combinations of sticks can create valid triangles and represent their findings using mathematical expressions. Each lesson is outlined in detail ...

Online

reSolve: Bifold Boxes

This lesson challenges students to use proportional reasoning to explain how changing the size of a square will affect the size of a box folded from that square. Students fold an origami box from a square of paper and record the dimensions of the resulting box. They then fold a box from a square of paper four times the ...

Online

reSolve: Geometry: Trapezium Pieces

This lesson explores different shapes that can be formed by cutting a trapezium in two with one straight line. Students are challenged to classify and name the shapes that are made, and justify their classifications based on the definitions and properties of shapes. The lesson is outlined in detail including curriculum ...

Online

reSolve: Monte Carlo Simulations

This sequence of two lessons explores how statistical techniques that rely on randomly generated data can be used to solve problems. In the first lesson, students compare different methods for calculating the area of an irregular shape, using the context of oil spill maps. They are introduced to the Monte Carlo method for ...

Online

reSolve: Trigonometric Trajectories

In this sequence of two lessons, students investigate trigonometric and Pythagorean relationships through two contexts: researching and building a model zipline ride and outlining a proposal for glider poles. In the first lesson, students apply trigonometric and Pythagorean relationships to investigate the dimensions of ...