Key Stage 3 Ratio and Proportion

Scale Factors and Maps

Use scale factors, scale drawings and maps to solve proportional problems.

Key idea

Find the multiplier or unit amount, then apply the same proportional change to the value you need.

What you will learn

Use scale factors confidently.

Use scale diagrams confidently.

Use maps confidently.

Use similar shapes confidently.

✓I can explain what scale factors and maps means.

✓I can choose a suitable method without being told.

✓I can show clear working and check my answer.

Worked example

Model method

Step 1

There are 3 + 5 = 8 parts.

Step 2

Each part is £40 ÷ 8 = £5.

Step 3

The shares are 3 × £5 and 5 × £5.

Answer

£15 and £25

Question 1

Share £60 in the ratio 2:3.

Question 2

5 pens cost £3. Find the cost of 12 pens.

Question 3

Increase £80 by 15%.

These are linked to the wider Ratio and Proportion topic for now.

A compact Ratio and Proportion summary with key facts, methods, reminders and common mistakes.

KS3 exam-style Ratio and Proportion questions with mixed practice, marks-style prompts and model answers.