Mathematics
Grade 7
15 min
Understanding ratios
Understanding ratios
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1
Introduction & Learning Objectives
Learning Objectives
Define what a ratio is and identify its components.
Express ratios in various forms (a:b, a/b, a to b).
Simplify ratios to their simplest form.
Identify and create equivalent ratios.
Distinguish between part-to-part and part-to-whole ratios.
Solve real-world problems involving ratios.
Have you ever wondered how chefs make sure their recipes taste the same every time, or how mapmakers shrink huge distances onto a small piece of paper? 🗺️ It's all thanks to ratios!
In this lesson, you'll discover the power of ratios – a fundamental concept for comparing quantities. We'll learn how to write, simplify, and use ratios to solve everyday problems, building a strong foundation for understanding proportions and rates later on.
Real-World Applicati...
2
Key Concepts & Vocabulary
TermDefinitionExample
RatioA ratio is a comparison of two quantities by division. It shows how much of one quantity there is compared to another.If there are 3 red apples and 2 green apples, the ratio of red apples to green apples is 3 to 2.
Terms of a RatioThe individual numbers or quantities being compared in a ratio are called its terms.In the ratio 3:2, '3' and '2' are the terms.
Forms of a RatioRatios can be written in three main ways: using the word 'to', using a colon, or as a fraction.The ratio of 3 red apples to 2 green apples can be written as '3 to 2', '3:2', or '3/2'.
Simplest Form of a RatioA ratio is in its simplest form when its terms have no common factors other than 1. This is similar to simplifying fractions.The...
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Core Formulas
Forms of a Ratio
A ratio comparing quantity 'a' to quantity 'b' can be written as: $a \text{ to } b$, $a:b$, or $\frac{a}{b}$
These are the three standard ways to express a ratio. The order of the terms is crucial and must match the order of the quantities being compared.
Simplifying Ratios
To simplify a ratio $a:b$, divide both terms by their Greatest Common Factor (GCF): $a:b = (a \div GCF) : (b \div GCF)$
This rule is used to express a ratio in its simplest form, making it easier to understand and compare. It's identical to simplifying fractions.
Finding Equivalent Ratios
To find an equivalent ratio for $a:b$, multiply or divide both terms by the same non-zero number $k$: $a:b = (a \times k) : (b \times k)$ or $a:b = (a \div k) : (b \div k)$...
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Sign Up Free to ContinueSample Practice Questions
Challenging
A movie is 2 minutes and 30 seconds long. A commercial is 45 seconds long. What is the ratio of the commercial's length to the movie's length in simplest form?
A.45:2.5
B.2:1
C.1:2
D.3:10
Challenging
A concrete mixture requires cement, sand, and gravel in the ratio 1:3:4. If a builder uses 12 bags of sand, how many bags of gravel will they need?
A.16
B.12
C.9
D.4
Challenging
The ages of two siblings are in the ratio 2:5. If the sum of their ages is 21, what is the age of the older sibling?
A.6
B.15
C.14
D.10
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