3.2.7

Two Ratios

Test yourself

Dealing With More Than One Ratio

You can scale up ratios by multiplying or dividing each part by the same number.

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Example

  • On a farm, the ratio of cows to sheep is 6 : 5. The ratio of sheep to pigs is 2 : 1. The total number of cows, sheep and pigs on the farm is 189. How many sheep are there on the farm?
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Example

  • Scale up the first ratio by 2 and the second ratio by 5 to get:
    • cows : sheep = 12 : 10, sheep : pigs = 10 : 5
    • So cows : sheep : pigs = 12 : 10 : 5.
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Example

  • Add up the number of parts and divide the total quantity by this number to get the value for each part:
    • Number of parts = 12 + 10 + 5 = 27
    • Value per part = 189 ÷ 27 = 7
    • Sheep is 10 parts so total number of sheep is 7 × 10 = 70.

Ratios

A ratio a : b means that for each 'a' of one thing there are 'b' of another. For example, if the ratio of boys to girls in a class is 3 : 4 that means that for every 3 boys there are 4 girls.

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Reducing a ratio

  • To reduce a ratio to a simpler form divide all parts by the same number.
  • It is in its simplest form if all parts are whole numbers and there are no more common factors left to divide by.
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Fractions and decimals

  • If a ratio contains decimals or fractions, multiply to get rid of them before simplifying the ratio.
  • If a ratio has mixed units convert both to the smaller unit and simplify.
  • Then remove the units from the ratio.
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Mixed unit ratios

  • If a ratio has mixed units convert both to the smaller unit and simplify.
  • Once both are using the same unit you can remove the units from the ratio.
    • 4.6kg : 2300g is the same as 4600g : 2300g
    • We can remove the unit and simplify to get 2:1
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Ratios as Linear Functions

  • See above for how you can convert from a ratio it a linear function.

Jump to other topics

1Number

1.1Using Numbers

1.1.1Equal Symbols

1.1.2Negative Numbers

1.1.3BIDMAS

1.1.4Inverse Operations

1.1.5End of Topic Test- Ordering

1.1.6Factors

1.1.7Multiples

1.1.8Highest Common Factor

1.1.9Lowest Common Multiple

1.1.10Number of Ways to Do a Task

1.1.11Number of Combinations

1.1.12Number of Ways To Arrange Objects

1.1.13End of Topic Test - Factors, Multiples & Combos

1.1.14Standard Form

1.1.15Ordinary Numbers to Standard Form

1.1.16Addition in Standard Form

1.1.17Subtraction in Standard Form

1.1.18Multiplication in Standard Form

1.1.19Division in Standard Form

1.1.20Exam-Style Questions - Standard Form & Primes

1.1.21Long Division

1.1.22Prime Numbers

1.1.23End of Topic Test - Standard Form & Long Division

1.2Fractions, Decimals & Percentages

1.2.1Adding Fractions

1.2.2Subtracting Fractions

1.2.3Multiplying Fractions

1.2.4Dividing Fractions

1.2.5Mixed Fractions

1.2.6Calculating Percentages of Numbers

1.2.7Calculating Fractions of Numbers

1.2.8Multiply Decimals

1.2.9Place Value

1.2.10Recurring Decimals

1.2.11Exam-Style Questions - Recurring Decimals

1.2.12Convert Fractions & Terminating Decimals

1.2.13Convert Recurring Decimals

1.2.14Convert Decimals & Percentages

1.2.15Compare Decimals

1.2.16Compare Fractions

1.2.17Exam-Style Questions - Percentages

1.2.18End of Topic Test - Fractions & Decimals

1.3Powers & Roots

1.3.1Powers

1.3.2Roots

1.3.3Indices Advanced

1.3.4Estimating Powers

1.3.5Estimating Roots

1.3.6Multiplying Powers

1.3.7Dividing Powers

1.3.8Power Raised to Power

1.3.9Fractions Raised to a Power

1.3.10Numbers Raised to Negative Powers

1.3.11Roots of Numbers

1.3.12Numbers to the Power of 1 & 0

1.3.13Surds

1.3.14Simplify Surds

1.3.15Rationalise Denominator

1.3.16Exam-Style Questions - Indices

1.3.17End of Topic Test - Powers & Roots

1.4Accuracy

1.4.1Decimal Rounding

1.4.2Significant Figure Rounding

1.4.3Estimation

1.4.4Truncation

1.4.5Limits of Accuracy

1.4.6Bounds Addition

1.4.7Bounds Subtraction

1.4.8Bounds Multiplication

1.4.9Bounds Division

1.4.10End of Topic Test - Rounding & Estimation

2Algebra

2.1Introduction to Algebra

2.1.1Algebra Basics

2.1.2Substituting Values

2.1.3Algebraic Vocabulary

2.1.4Collecting Terms

2.1.5End of Topic Test - Algebra Basics & Power Rules

2.1.6Expanding Brackets I

2.1.7Common Factors

2.1.8Expanding Brackets II

2.1.9Rearrange For x

2.1.10Rearrange with Powers

2.1.11Exam-Style Questions - Basics of Algebra

2.1.12End of Topic Test - Expanding & Rearranging

2.2Manipulating Algebra

2.2.1How to Factorise

2.2.2Factorising Quadratics

2.2.3Algebraic Fractions - Addition & Subtraction

2.2.4Algebraic Fractions - Multiplication & Division

2.3Proofs & Functions

2.3.1Identities & Proofs

2.3.2Exam-Style Questions - Algebraic Proof

2.3.3End of Topic Test - Algebra & Proofs

2.3.4Functions

2.3.5Combine Functions

2.3.6Composite Functions

2.3.7Inverse Functions

2.4Straight Line Graphs

2.4.1Straight Line Graphs

2.4.2y = mx + c

2.4.3Grad + YIntercept

2.4.4Exam-Style Questions - Straight Line Graphs

2.4.5End of Topic Test - Functions & Straight Lines

2.5Common Graphs

2.5.1Shape of Quadratic Graphs

2.5.2Roots of a Quadratic Graph

2.5.3Completing Squares

2.5.4Turning Points

2.5.5Common Functions 1

2.5.6Common Functions 2

2.5.7Trigonometric functions

2.5.8End of Topic Test - Common Graphs

2.6Transformations & Tangents

2.6.1Transformations

2.6.2Tangent on a Circle

2.7Properties of Graphs

2.7.1Estimate Gradient

2.7.2Estimate Area

2.7.3Represent Gradient & Area

2.7.4Distance-Time Graph

2.7.5Velocity-Time Graph

2.7.6End of Topic Test - Transformations & Graphs

2.8Solving Equations

2.8.1Solve Linear Equations

2.8.2Linear Equations with Fractions

2.8.3Solve Linear Equations Graphically

2.8.4Quadratic ±

2.8.5Factorise Quadratics

2.8.6Quadratic Formula

2.8.7Complete the Square

2.8.8Solve Quadratics Graphically

2.8.9End of Topic Test - Solving Equations

2.8.10Simultaneous Equations

2.8.11Quadratic Simultaneous Equations

2.8.12Simultaneous Equations - Graphs

2.8.13Simultaneous Equations - Word Problems

2.8.14Approximate Solutions - Number of Iterations

2.8.15Approximate Solutions - Iterations to 1 DP

2.8.16Approximate Solutions - Iteration Formula

2.8.17Exam-Style Questions - Simultaneous Equations

2.8.18End of Topic Test - Simultaneous Equations

2.9Inequalities

2.9.1Solving Inequalities

2.9.2Solving Double Inequalities

2.9.3Solving Quadratic Inequalities

2.9.4Representing Inequalities

2.9.5Exam-Style Questions - Inequalities

2.9.6End of Topic Test - Inequalities

2.10Sequences

2.10.1Nth Term Rules

2.10.2Recurrence Relationships

2.10.3Find Nth Term in Linear Sequence

2.10.4Check If a Number is In a Sequence

2.10.5Exam-Style Questions - Sequences

2.10.6Arithmetic & Geometric Progressions

2.10.7Key Sequences

2.10.8Quadratic Sequences

2.10.9Find Nth Term in Quadratic Sequence

2.10.10Exam-Style Questions - Geometric Series

2.10.11End of Topic Test - Sequences

3Ratio

3.1Ratios in Practice

3.1.1Converting Between Units

3.1.2Formula Triangles

3.1.3Scale Factors

3.1.4Ratios in Shapes

3.2Manipulating Ratios

3.2.1Simplifying Ratios

3.2.2Turn Ratios into Equations

3.2.3Ratio Notation & Reduction

3.2.4End of Topic Test - Units & Ratios

3.2.5Part : Part Ratio

3.2.6Part : Whole Ratio

3.2.7Two Ratios

3.2.8Differences in Ratios

3.2.9Fractions in Ratios

3.2.10Numbers as Fractions

3.2.11Ratios to Fractions

3.2.12Exam-Style Questions - Ratios

3.2.13End of Topic Test - Fractions & Ratios

3.3Percentage & Interest

3.3.1Convert Percentages to Decimals

3.3.2Convert Percentages to Fractions

3.3.3Find the Percentage

3.3.4More/Less Percentage

3.3.5Price from Percentage Change

3.3.6Calculate Percentage Change from Price

3.3.7End of Topic Test - Percentages

3.3.8Profit & Interest & Discount

3.3.9Original Price after Discounts

3.3.10Simple Interest

3.3.11Compound Growth & Decay

3.3.12Compound Interest

3.3.13Compound Interest - After How Many Days?

3.3.14End of Topic Test - Percentages in Finance

3.4Proportion

3.4.1Proportion

3.4.2Direct Proportion

3.4.3Inverse Proportion

3.4.4Exam-Style Questions - Proportionality

3.5Gradient

3.5.1Gradient on a Straight Line

3.5.2Direct & Inverse Proportions as Graphs

3.5.3Gradient of a Curve

3.5.4Positive & Negative Gradients

3.5.5End of Topic Test - Proportion & Gradient

4Geometry

4.1Introduction to Geometry

4.1.1Geometry Basics

4.1.2Geometry Basics 2

4.1.3Regular Polygons

4.1.4Triangles & Angles

4.1.5Midpoint

4.1.6Bisectors & Perpendiculars

4.1.7Locus

4.1.8Angle rules

4.1.9Parallel Angle Rules

4.1.10Angles in a Polygon

4.1.11Angles in a Triangle

4.1.12Exam-Style Questions - Angles in Shapes

4.1.13End of Topic Test - Geometry

4.2Triangles & Quadrilaterals

4.2.1Types of Triangle

4.2.2Angles & Triangles

4.2.3Congruence

4.2.4Similarity

4.2.5Quadrilaterals

4.3Transformations

4.3.1Types of Transformations

4.3.2Invariant Points

4.3.3Effects of Transformations

4.3.4Exam-Style Questions - Reflection

4.4Circle Basics

4.4.1Properties of a Circle 1

4.4.2Chords

4.4.3Properties of a Circle 2

4.4.4Area of a Circle

4.4.5Circumference of a Circle

4.4.6Fractions of Circles

4.4.7Exam-Style Questions - Circle Formulae

4.4.8End of Topic Test - Triangles & Circles

4.5Circle Theorems

4.5.1Perpendicular Bisector of a Chord

4.5.2Angle at the Centre

4.5.3Angle of a Semicircle

4.5.4Opposite Angles in Cyclic Quadrilaterals

4.5.5Tangent Lengths

4.5.6Angle in the Same Segment

4.5.7Alternate Segment Theorem

4.5.8Exam-Style Questions - Circle Theorems

4.6Measurements & Units

4.6.1Length

4.6.2Area

4.6.3Volume

4.6.4Capacity

4.6.5Time

4.6.6Money

4.6.7Mass

4.6.8Bearings

4.6.9Scale Factor & Enlargement

4.6.10Exam-Style Questions - Enlargements

4.7Calculating Area

4.7.1Area of 2D Shapes

4.7.2Exam-Style Questions - Area

4.7.3End of Topic Test - Circle Theorems, Units & Area

4.8Triangle Formulae

4.8.1Pythagoras' Theorem

4.8.2Pythagoras in 3D

4.8.3Trigonometry

4.8.4Exact Values

4.8.5Sine Rule

4.8.6Cosine Rule

4.8.7Area of a Triangle

4.8.8Exam-Style Questions - Trigonometry & Area

4.93D Shapes

4.9.1Types of 3D Shape

4.9.2Plans & Elevations

4.9.3Nets

4.9.4Volume of 3D Shapes

4.9.5Volume of a Cuboid

4.9.6Volume of a Cylinder

4.9.7Volume of a Sphere

4.9.8Volume of a Hemisphere

4.9.9Volume of a Cone

4.9.10Volume of a Pyramid

4.9.11Surface Area & Composite Shapes

4.9.12Surface Area of a Cuboid

4.9.13Surface Area of a Cylinder

4.9.14Surface Area of a Sphere/Hemisphere

4.9.15Surface Area of a Cone

4.9.16Exam-Style Questions - Volume

4.10Vectors

4.10.1Vectors Introduction

4.10.2Vectors

4.10.3Translation

4.10.4Scalar

4.10.5Exam-Style Questions - Vectors

4.10.6End of Topic Test - Trigonometry, Shapes & Vectors

5Probability

5.1Introduction to Probability

5.1.1Randomness & Fairness

5.1.2Sum of Probabilities

5.1.3Relative & Expected Frequency

5.1.4Frequency Tables

5.1.5Using Frequency Trees

5.1.6Complete Frequency Trees

5.2Representing Probabilities

5.2.1Probability

5.2.2Probability Scale

5.2.3Sample Space Diagrams

5.2.4Sets

5.2.5Venn Diagrams

5.2.6Probabilities in Venn Diagrams

5.2.7Exam-Style Questions - Venn Diagrams

5.3Probability Calculations

5.3.1Theoretical Probabilities

5.3.2Multiple Events

5.3.3Probability Calculations

5.3.4Dependent Events

5.3.5Independent Events

5.3.6Probability Tree Diagram

5.3.7Complex Tree Diagrams

5.3.8Conditional Probability

5.3.9Conditional Probability From a Two Way Table

5.3.10Conditional Probability Venn Diagrams

5.3.11Conditional Probability Tree Diagrams

5.3.12Exam-Style Questions - Probability

5.3.13End of Topic Test - Probability

6Statistics

6.1Introduction to Statistics

6.1.1Statistics Basics

6.1.2Statistics Key Terms

6.1.3Frequency Tables

6.1.4Exam-Style Questions - Statistics & Probability

6.2Charts & Diagrams

6.2.1Bar Charts

6.2.2Pie Charts

6.2.3Stem & Leaf Diagrams

6.2.4Back to Back Stem & Leaf Diagrams

6.2.5End of Topic Test - Statistics

6.2.6Pictograms

6.2.7Time Series Graphs

6.2.8Histograms

6.2.9Histograms 2

6.2.10Frequency Polygons

6.2.11Cumulative Frequency

6.2.12Cumulative Frequency 2

6.2.13Scatter Graphs

6.2.14Scatter Graphs - Predictions

6.2.15Correlation & Causation

6.2.16Exam-Style Questions - Cumulative Frequency

6.3Comparing Datasets

6.3.1Comparing Datasets

6.3.2End of Topic - Datasets

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Part : Whole Ratio

Differences in Ratios