# Spatial Reasoning: Right Angles

Australian curriculum number (ACMMG141)

Students build their ability to create and identify right angles. They are challenged to reason mathematically and form generalisations.

This sequence is for students who:

• have been introduced to right angles.
• can identify and name polygons with up to eight sides.
• are familiar with identifying and describing patterns in data that result from multiplication.

### Lesson 1: How Many Right Angles?

Students create right angles using two ice-cream sticks. They discover they can make one, two or four right angles, but they cannot make three. They explore the number of right angles that can be made with any number of sticks.

### Lesson 2: Six Internal Right Angles

Students are asked to construct a polygon with exactly six internal right angles. They see that it is possible to make an octagon with six right angles and two angles of 270°. Students sort the octagons based on the number of right angles that separate the 270° angles.

Last updated June 20 2020.