Maths5ATEXTBOOK

Dr Lai Chee ChongTan Kim Lian

ConsultantDr Spario Soon

•APPROVED

BYMINISTRY OF EDU

CATION

•

for use from 2008–2

016

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PREFACE

is a series of textbooks and accompanying workbooks specially written to meet the mathematical needs of primary school pupils.

This series adopts a learner-centred and lively approach to teaching Mathematics.

Each chapter in the textbook begins with a warm-up section which creates an opportunity for class discussion and interaction. Illustrations in each chapter enhance pupils’ understanding of the mathematical concepts. Stimulating questions and fun activities challenge pupils to think critically and creatively. Learning outcomes are summarised at the end of the chapter to provide a quick review.

Through , pupils can become proficient in Mathematics while learning to appreciate the beauty and power of the subject.

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ABOUT THE BOOK

Each chapter in the textbook has the following features:

EnrichmentEngages pupils with fun-filled activities that promote critical and creative thinking skills.

Warm-UpCreates opportunity for class discussion and interaction.

You will learn toHighlights the learning outcomes of the chapter.

Types of activities foundin ‘Enrichment’:

: Pair/Group activity

: Problem Solving activity

: IT activity

Self-testA quick assessment of pupils’ understanding at the end of each chapter.

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Let’s See In Everyday LifeRelates what’s taught to daily scenarios.

Stop-Think-GoEncourages pupils to think further.

Work It OutActs as a quick review.

Directs pupils to the appropriate worksheet.

Wrap It UpSummarises the main points learnt in the chapter.

Indicates the use of calculator in the book

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CONTENTS

CHAPTER 1 Numbers up to 10 000 000 1

A Numbers and place values 2 B Comparing and ordering 8 C Rounding off and estimation 11

CHAPTER 2 Operations of whole numbers 19

A Multiply by tens, hundreds and thousands 20 B Divide by tens, hundreds and thousands 25 C Estimation in calculations 29 D Order of operations 32 E Word problems 37

CHAPTER 3 Fractions I 45

A Fraction and division 46 B Addition and subtraction of unlike fractions 50 C Addition and subtraction of mixed numbers 55

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CHAPTER 4 Fractions II 65

A Multiplication of fractions 66 B Divide a proper fraction by a whole number 72 C Word problems 74

CHAPTER 5 Ratios 83

A Simple ratios 84 B Equivalent ratios 90 C Ratios of three quantities 95

CHAPTER 6 Area of triangle 103

A Base and height of a triangle 104 B Area of a triangle 108

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Discover Maths 1 …………

1 Numbers up to 10 000 000

What’s the largest number you have learnt so far?

100 000

In this chapter, you will learn to:

• read and write numbers up to 10 000 000;• recognise the place values of millions, hundred thousands,

ten thousands, thousands, hundreds, tens and ones;• compare and order numbers up to 10 000 000;• round off numbers to the nearest 1000;• estimate answers in calculations;• use the calculator to check for reasonableness of answers.

If I tell you that there are as many as 700 000 ants in one ant colony, do you know how many ants there are in two such colonies?

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2 Chapter 1 Numbers up to 10 000 000…………

The diagram below shows a bead counter.

195 326 has 6 digits.

We can see that 195 326 has 1 hundred thousand, 9 ten thousands, 5 thousands, 3 hundreds, 2 tens and 6 ones.

1 hundred thousand = 100 000 9 ten thousands = 90 000 5 thousands = 5000 3 hundreds = 300 2 tens = 20 6 ones = 6

195 326 = 100 000 + 90 000 + 5000 + 300 + 20 + 6

195 326 is written as one hundred and ninety-five thousand, three hundred and twenty-six in words.

Hundred Thousands

TenThousands

Thousands Hundreds Tens Ones

1 9 5 3 2 6

Hundred Thousands

TenThousands

Thousands Hundreds Tens Ones

Numbers and place valuesA

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Discover Maths 3 …………

Hundred Thousands

TenThousands

Thousands Hundreds Tens Ones

What is 10 000 more than 195 326?

9 ten thousands + 1 ten thousand = 10 ten thousands

The digit in the ten thousands place is now 0 because 10 ten thousands= 1 hundred thousand.

So, 10 000 more than 195 326 is 205 326.

205 326 = 200 000 + 5000 + 300 + 20 + 6

205 326 is written as two hundred and fi ve thousand, three hundred and twenty-six in words.

Hundred Thousands

TenThousands

Thousands Hundreds Tens Ones

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4 Chapter 1 Numbers up to 10 000 000…………

Look at the place value table below.

The digit 7 is in the ones place. Its value is 7.The digit 5 is in the tens place. Its value is 50.The digit 2 is in the hundreds place. Its value is 200.The digit 4 is in the thousands place. Its value is 4000.The digit 6 is in the ten thousands place. Its value is 60 000.The digit 9 is in the hundred thousands place. Its value is 900 000.

964 257 = 900 000 + 60 000 + 4000 + 200 + 50 + 7

Look at the place value table below. How do we name 1000 thousands?

Hundred Thousands

TenThousands

Thousands Hundreds Tens Ones

9 6 4 2 5 7

What is 1 more than 999 999?

? Hundred Thousands

TenThousands

Thousands Hundreds Tens Ones

1 0 0 0 0 0 0

It is 10 hundred thousands.

10 hundred thousands = 1 million

Millions Hundred Thousands

TenThousands

Thousands Hundreds Tens Ones

1 0 0 0 0 0 0

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