GCSE Ratio and Proportion

Growth and Decay

Learn growth and decay 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 growth and decay meaning confidently.

Use growth and decay representations confidently.

Use growth and decay methods confidently.

Use growth and decay applications confidently.

✓I can explain what growth and decay 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.