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)
What a learner can do afterwards
- 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
1 · Read
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.
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.
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.
2 · Watch
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Where it sits
Learn first
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.