GCSE Ratio and Proportion

Similarity

Learn similarity as part of use multiplicative reasoning in ratio, proportion, scaling, rates, similarity and real-life graph contexts.

Key idea

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

What you will learn

Use similarity meaning confidently.

Use similarity representations confidently.

Use similarity methods confidently.

Use similarity applications confidently.

✓I can explain what similarity 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.

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