---
title: "Ratio and proportion vocabulary"
description: "Know and use the vocabulary of ratio and proportion — ratio, proportion, percentage, scale, equivalent, unequal, relative size, part-to-part, part-to-whole, and out of — and understand the difference "
canonical: https://lightmysky.com/learn/mathematics/ratio-and-proportion-vocabulary-mt_ESgc4YBw-a
source: https://lightmysky.com/learn/mathematics/ratio-and-proportion-vocabulary-mt_ESgc4YBw-a.md
retrieved: 2026-09-02
---

> **Agent view.** This is the Markdown twin of the page, for tools and assistants.
> When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md
> API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md
> Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt
> Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json
> Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`.

# Ratio and proportion vocabulary

Know and use the vocabulary of ratio and proportion — ratio, proportion, percentage, scale, equivalent, unequal, relative size, part-to-part, part-to-whole, and out of — and understand the difference between ratio (comparing parts to parts) and proportion (comparing a part to the whole)

Subject: Mathematics · Area: Ratio & Proportion · Ages 9 to 11
Page: https://lightmysky.com/learn/mathematics/ratio-and-proportion-vocabulary-mt_ESgc4YBw-a

## Ready when they can

- Explain the difference between a 'ratio' and a 'proportion' using a concrete example like mixing paint
- Use 'per cent' correctly and convert between fractions, decimals, and percentages in context
- Define 'scale factor' and use it to describe how a shape has been enlarged or reduced

## Lesson: Ratio and proportion: comparing parts

A ratio compares one part to another part. A proportion compares one part to the whole thing. They sound alike, but they answer different questions.

*(drawing: Mia mixes 3 cups of red paint with 2 cups of yellow paint. The ratio of red to yellow is 3:2.)*

**Example.** Mia's paint has 5 cups in total: 3 red and 2 yellow. The ratio of red to yellow is 3:2, a part-to-part comparison. But the proportion of red in the whole mix is 3 out of 5, which is 60 percent. That's a part-to-whole comparison.

A scale factor tells you how many times bigger or smaller a shape becomes. A scale factor of 2 doubles every length. A scale factor of one half shrinks every length by half.

The word 'per cent' means 'out of 100'. So 60% is 60 out of 100, which is the same as the fraction 3 out of 5 and the decimal 0.6. To change a fraction into a percentage, picture the whole split into 100 equal parts and count how many of them are shaded. To go the other way, write the percentage over 100 and simplify it.

**Recap.** Ratio compares part to part, proportion compares part to whole, percent means out of 100, and scale factor shows how much a shape grew or shrank.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Understanding Percentages](https://lightmysky.com/learn/mathematics/understanding-percentages-mt_ZM9mhHsyYZ)

## Opens up

- [Scale and similar shapes](https://lightmysky.com/learn/mathematics/scale-and-similar-shapes-mt_2OtRUM_0zW)
- [Ratio Problems](https://lightmysky.com/learn/mathematics/ratio-problems-mt_h0gJcSuwdL)
- [Calculating Percentages](https://lightmysky.com/learn/mathematics/calculating-percentages-mt_PNSyfH56eQ)