# subtraction

## Investigating Integers

- Units of Work
- Number and Algebra
- Level Four

This unit begins with Freudenthal’s (1983) annihilation model for demonstrating the addition and subtraction of integers then goes on to introduce other representations. It is designed for students working at Stage 7 of the Number Framework who are able to choose appropriately from a broad range of mental strategies to estimate answers and solve addition and subtraction.

## Three Circles II

- Units of Work
- Number and Algebra
- Level Four

In this unit students are asked to investigate mathematical relationships when they select various numbers into be used in 3 circle configuration below and in 6 circle configurations. They will explore both whole number and fractional numbers as they consider how various configurations impact on the relationships between numbers.

## Difference Magic Squares

- Problem Solving Activities
- Number and Algebra
- Level Six

This is a problem from the number and algebra strand.

## Gulls

- Problem Solving Activities
- Number and Algebra
- Level Three

Select the appropriate number operation(s) to solve problems.

Devise and use problem solving strategies (act it out, draw a picture, organised list)

## The 500 Problem

- Problem Solving Activities
- Number and Algebra
- Level Three

Explain face, place and total value of numbers

Solve 3-digit subtraction problems

Devise and use problem solving strategies (guess and check, think logically)

## Shopping

- Problem Solving Activities
- Number and Algebra
- Level Two

Give change for sums of money

Solve subtraction problems presented in different forms

Devise and use problem solving strategies to explore situations mathematically (guess and check, use drawing, use equipment, be systematic, act it out).

## Three Circles I

- Units of Work
- Number and Algebra
- Level Three

In this unit students are asked to investigate mathematical relationships when they select various numbers into be used in 3 circle configuration below and in 6 circle configurations. They will explore both whole number and fractional numbers as they consider how various configurations impact on the relationships between numbers.

## Addition and Subtraction Pick n Mix

- Units of Work
- Number and Algebra
- Level Three

In this unit we look at a range of strategies for solving addition and subtraction problems with whole numbers with a view to students anticipating from the structure of a problem which strategies might be best suited.

## The Difference Bar 2

- Units of Work
- Number and Algebra
- Level Three

This unit introduces students to "The Difference Bar" digital learning object, a tool to help students work out the difference between two numbers by breaking numbers into parts.

This unit is for students at Stage 6-Advanced Additive of the Number Framework, Curriculum Level 3, i.e. students who have developed more than one part-whole strategy for addition and subtraction and can use these strategies to solve problems involving large numbers.

This digital learning object has two versions, one where difference problems are generated and one where students and teachers can make up their own difference problems. The problems at this level involve solving the difference between 2 two-digit numbers.

## The Take-Away Bar 2

- Units of Work
- Number and Algebra
- Level Three

This unit introduces students to "The Take-Away Bar" digital learning object, a tool to help students solve subtraction problems by breaking numbers into parts.

This unit is for students at Stage 6-Advanced Additive of the Number Framework, Curriculum Level 3, i.e. students who have developed more than one part-whole strategy for addition and subtraction and can use these strategies to solve subtraction problems involving large numbers.

This digital learning object has two versions, one where subtraction problems are generated and one where students and teachers can make up their own subtraction problems. The problems at this level involve subtracting a two-digit number from a larger two-digit number.