# Space and Geometry – Properties of Geometric Figures

## Strategy

Students can:

• use angle properties of a triangle to determine angle size
• classify quadrilaterals according to their properties.

## Activities to support the strategy

### Activity 1: quadrilaterals

Display transparent coloured plastic 2D shapes (parallelogram, rhombus, square, rectangle, pentagon, hexagon and octagon) on whiteboard or on overhead projector.

• The teacher reads short descriptions of each shape from labels and matches them to the correct shape displayed on the whiteboard.

• The teacher moves labels to bottom of whiteboard (modify for overhead projector). The teacher or students read shape description labels. Chosen students match labels to correct shapes.

• The teacher has worksheet with shape descriptions and matching unmarked diagrams of shapes copied onto an overhead. The teacher models how to read the description and mark each property on the diagram.

• The teacher needs to prepare same size pairs of cards in two different colours (one card with the shape and the other card in a different colour with the description). All the definitions are on the same colour card and all the diagrams are on a different colour card. (See example below.)

• Students play Concentration, turning over two cards, one of each colour. Students read descriptions as they turn them over.
• Guessing Games – Teacher reads clues from description cards. Students name the correct shape. Repeat this activity in pairs.
• Students complete cloze activity on each shape, e.g.

#### Enquiry and elimination game

Display shape cards from the matching game and give chosen student one definition card which is not shown to the group. The student reads the definition and other students have to identify the shape.

The successful student then has a turn to read the description.

View/print

#### What am I? (twenty questions)

Display shape cards from the matching game and give one student a definition card which is not shown to the group. Students ask questions about the shape. The chosen student can only answer: ‘yes’, ‘no’ or ‘sometimes’, e.g.

Does it have any right angles? If the chosen card is a trapezium the answer would have to be sometimes as only some trapeziums have right angles. Students continue playing until a child guesses the correct shape or the group has asked 20 questions, whichever occurs first.

#### Barrier Game

Each student has 8 -10 drawings of the 2D quadrilaterals and polygons studied (a variety of the same shape but in different forms should be included) with parts of a description underneath. Their partner has the same pictures but with different parts of the definition. Students have to write the complete definition of each shape, getting the missing information from their partner. For example:

### Activity 2: triangle properties

1. Students can investigate triangle properties using GeoGebra resources found in the Geometers Warehouse, Stage 4

2. Students can use the Trigonometry - measuring with triangles learning object to investigate the properties of right-angled triangles.

## References

### Australian curriculum

ACMMG166: Demonstrate that the angle sum of a triangle is 180° and use this to find the angle sum of a quadrilateral. ACMMG202: Establish properties of quadrilaterals using congruent triangles and angle properties, and solve related numerical problems using reasoning.

### NSW syllabus

MA4-17MG: Classifies, describes and uses the properties of triangles and quadrilaterals, and determines congruent triangles to find unknown side lengths and angles.