# Ratio, proportion and percentages

## Introduction

This unit is from our archive and it is an adapted extract from Open mathematics (MU120) which is no longer in presentation. If you wish to study formally at The Open University, you may wish to explore the courses we offer in this curriculum area [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]

The topics in this unit, ratios, proportion and percentages, are concerned with dividing something into parts. For example, if there are 200 people living in a small village, and 50 of these are children, this could be expressed as a percentage:

25% of the village population are children;

or as a ratio:

one in every four people is a child or there is 1 child for every three adults;

or a proportion:

the proportion of children in the village population is a quarter.

One difficulty that some people find with these topics is knowing when to multiply and when to divide. This module revises the relevant techniques and helps you to apply them logically.