Algebra: Think of a Number

Australian curriculum number (ACMNA190; ACMNA191; ACMNA192)

Students come to appreciate the power of algebra for generalising results from arithmetic. They connect arithmetic operations with algebraic notation and visualisations. The lesson begins with an observation made using arithmetic that students then justify and extend using algebra.

This lesson is designed to consolidate skills in algebra, including collecting like terms and expanding and factorising using the distributive law. It emphasises the importance of algebra for generalising and justifying arithmetic results. It is assumed that students have some familiarity with algebraic notation.

Lesson 1: Think of a Number – Linear Equations

Think of a number (THOAN) activities show how algebraic reasoning can be used to explain and formulate problems in which chains of operations always result in the same outcome regardless of the number chosen. Students are introduced to THOANs involving simple linear operations, and use algebraic simplification to explain why the THOAN works. They are then asked to complete a THOAN when given some starting operations and, finally, to make and test their own.

Last updated June 21 2020.