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1.31 Problems with two unknowns

Created on 16 October 2018 by ncetm_administrator
Updated on 16 October 2018 by ncetm_administrator

Introduction

Equip children with strategies for solving problems with two unknowns, including using the bar model to represent relationships between known numbers, and working systematically.

Teaching points

• Teaching point 1: Problems with two unknowns can have one solution or more than one solution (or no solution). A relationship between the two unknowns can be described in different ways, including additively and multiplicatively.

• Teaching point 2: Model drawing can be used to expose the structure of problems with two unknowns.

• Teaching point 3: A problem with two unknowns has only one solution if the sum of the two unknowns and the difference between them is given (‘sum-and-difference problems’) or if the sum of the two unknowns and a multiplicative relationship between them is given (‘sum-and-multiple problems’).

• Teaching point 4: Other problems with two unknowns have only one solution.

• Teaching point 5: Some problems with two unknowns can’t easily be solved using model drawing but can be solved by a ‘trial-and-improvement’ approach; these problems may have one solution, several solutions or an infinite number of solutions.

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