# Scale factors, ratio and proportional reasoning

Spine 2: Multiplication and Division – Topic 2.27

Primary KS2 Year 6
Mastery PD Materials

### Introduction

Use bar modelling and ratio grids to reason about multiplicative relationships between two or more cardinal quantities, and explore correspondence problems. Extend understanding of scaling measures to make and interpret maps and scale/compare the dimensions of similar shapes.

### Teaching points

• Teaching point 1: Multiplication and division can be used to calculate unknown values in correspondence (cardinal comparison) problems.

• Teaching point 2: Multiplication and understanding of correspondence can be used to calculate the number of possible combinations of items.

• Teaching point 3: Scaling can be used to make and interpret maps.

• Teaching point 4: There is a proportional relationship between the dimensions of similar shapes; if the scale factor and the dimensions of one of the shapes is known, the dimensions of the similar shape can be calculated; if the dimensions of both of the shapes are known, the scale factor can be calculated.