• Mastery PD Materials

## Using equivalence and the compensation property to calculate

Spine 1: Number, Addition and Subtraction – Topic 1.29

### Introduction

Explore the effect on the sum of changing the value of one or both addends; explore the effect on the difference of changing the value of the minuend, the subtrahend or both. Apply knowledge of compensation properties and inverse operations to calculate and balance equations.

### Teaching points

• Teaching point 1: If one addend is increased and the other is decreased by the same amount, the sum stays the same. (same sum)

• Teaching point 2: If one addend is increased (or decreased) and the other is kept the same, the sum increases (or decreases) by the same amount.

• Teaching point 3: If the minuend and subtrahend are changed by the same amount, the difference stays the same. (same difference)

• Teaching point 4: If the minuend is increased (or decreased) and the subtrahend is kept the same, the difference increases (or decreases) by the same amount.

• Teaching point 5: If the minuend is kept the same and the subtrahend is increased (or decreased), the difference decreases (or increases) by the same amount.

• Teaching point 6: The value of the expressions on each side of an equals symbol must be the same; addition and subtraction are inverse operations. We can use this knowledge to balance equations and solve problems.

• Primary
• KS2
• Year 5