Ratio & Proportion
Simplify ratios, divide a quantity in a given ratio, and solve direct and inverse proportion problems.
Overview
A ratio compares two or more quantities, and proportion describes how they change together. Building on Year 7, Year 8 students simplify ratios (including those with units), divide a quantity into more than two parts, and solve direct proportion problems using the unitary method. They also meet inverse proportion, where one quantity goes down as the other goes up.
What You Will Learn
- Simplify ratios, including ratios with units and ratios in the form 1 : n
- Divide a quantity into a given ratio of two or more parts
- Use the unitary method to solve direct proportion problems
- Recognise and solve simple inverse proportion problems
- Use ratio and proportion in real contexts such as recipes, maps and best-buy comparisons
Key Vocabulary
Common Mistakes to Avoid
- Not converting to the same units before simplifying a ratio
- Adding the ratio parts incorrectly when sharing a quantity
- Treating inverse proportion like direct proportion
- Forgetting to find the value of one part before scaling up
What Comes Next
In Year 9 and at IGCSE this develops into proportion as an equation, scale drawings, and compound measures such as speed and density, within the IGCSE Number topic.
Frequently Asked Questions
How do I divide an amount in a ratio?
Add the parts of the ratio to find the total number of parts, divide the amount by that total to find one part, then multiply for each share. To share $40 in the ratio 3 : 2, there are 5 parts, one part is $8, so the shares are $24 and $16.
What is the difference between direct and inverse proportion?
In direct proportion, as one quantity increases the other increases at the same rate — more items cost more. In inverse proportion, as one increases the other decreases — more workers take less time to finish a job.
Study This Topic
Topic Details
- Stage
- Year 8
- Strand
- Number
- Framework ref
- 8Nf
- Difficulty
- Medium
Build strong foundations in Ratio & Proportion
A free trial class with Teacher Rig helps your Year 8 child master Ratio & Proportion now — so IGCSE Maths feels familiar, not frightening, later.
Heading toward IGCSE? See how Ratio & Proportion develops in IGCSE Number (Cambridge 0580) →