TOÁN TIẾNG ANH CHO HỌC SINH LỚP 10

Everything Maths
Grade 10 Mathematics

Version 1 – CAPS

by Siyavula and volunteers


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Authors List
This book is based upon the original Free High School Science Text which was entirely written by
volunteer academics, educators and industry professionals. Their vision was to see a curriculum aligned
set of mathematics and physical science textbooks which are freely available to anybody and exist under
an open copyright license.

Siyavula core team
Neels van der Westhuizen; Alison Jenkin; Leonard Gumani Mudau; Marina van Zyl; Helen Robertson; Carl Scheffler; Nicola du Toit; Josephine Mamaroke Phatlane; William Buthane Chauke; Thomas
Masango

Original Free High School Science Texts core team
Mark Horner; Samuel Halliday; Sarah Blyth; Rory Adams; Spencer Wheaton

Original Free High School Science Texts editors
Jaynie Padayachee; Joanne Boulle; Diana Mulcahy; Annette Nell; René Toerien; Donovan Whitfield

Siyavula and Free High School Science Texts contributors
Sarah Abel; Dr. Rory Adams; Andrea Africa; Matthew Amundsen; Ben Anhalt; Prashant Arora; Amos
Baloyi; Bongani Baloyi; Raymond Barbour; Caro-Joy Barendse; Richard Baxter; Tara Beckerling; Tim van
Beek; Jennifer de Beyer; Dr. Sarah Blyth; Sebastian Bodenstein; Martin Bongers; Gareth Boxall; Stephan
Brandt; Hannes Breytenbach; Alex Briell; Wilbur Britz; Graeme Broster; Craig Brown; Deanne de Bude;
Richard Burge; Bianca Böhmer; George Calder-Potts; Eleanor Cameron; Richard Case; Sithembile Cele;
Alice Chang; Richard Cheng; Fanny Cherblanc; Dr. Christine Chung; Brett Cocks; Stefaan Conradie;
Rocco Coppejans; Tim Craib; Andrew Craig; Tim Crombie; Dan Crytser; Dr. Anne Dabrowski; Laura
Daniels; Gareth Davies; Sean Dobbs; Buhle Donga; William Donkin; Esmi Dreyer; Matthew Duddy;
Fernando Durrell; Dr. Dan Dwyer; Frans van Eeden; Alex Ellis; Tom Ellis; Andrew Fisher; Giovanni
Franzoni; Ingrid von Glehn; Tamara von Glehn; Lindsay Glesener; Kevin Godby; Dr. Vanessa Godfrey; Terence Goldberg; Dr. Johan Gonzalez; Saaligha Gool; Hemant Gopal; Dr. Stephanie Gould;
Umeshree Govender; Heather Gray; Lynn Greeff; Carine Grobbelaar; Dr. Tom Gutierrez; Brooke Haag;
Kate Hadley; Alex Hall; Dr. Sam Halliday; Asheena Hanuman; Dr. Melanie Dymond Harper; Dr.
Nicholas Harrison; Neil Hart; Nicholas Hatcher; Jason Hayden; Laura Hayward; Dr. William P. Heal;
Pierre van Heerden; Dr. Fritha Hennessy; Shaun Hewitson; Millie Hilgart; Grant Hillebrand; Nick
Hobbs; Chris Holdsworth; Dr. Benne Holwerda; Dr. Mark Horner; Robert Hovden; Mfandaidza Hove;
Jennifer Hsieh; Laura Huss; Rowan Jelley; Grant Jelley; Clare Johnson; Luke Jordan; Tana Joseph; Dr.
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Lebaka; Dr. Marco van Leeuwen; Dr. Tom Leinster; Henry Liu; Christopher Loetscher; Mike Loseby;
Amandla Mabona; Malothe Mabutho; Stuart Macdonald; Dr. Anton Machacek; Tshepo Madisha; Batsirai Magunje; Dr. Komal Maheshwari; Michael Malahe; Masoabi Malunga; Kosma von Maltitz; Masilo
Mapaila; Bryony Martin; Nicole Masureik; John Mathew; Dr. Will Matthews; Chiedza Matuso; JoEllen
McBride; Nikolai Meures; Riana Meyer; Filippo Miatto; Jenny Miller; Abdul Mirza; Mapholo Modise;
Carla Moerdyk; Tshwarelo Mohlala; Relebohile Molaoa; Marasi Monyau; Asogan Moodaly; Jothi Mood-


ley; Robert Moon; Calvin Moore; Bhavani Morarjee; Kholofelo Moyaba; Nina Gitau Muchunu; Kate

Murphy; Emmanuel Musonza; Tom Mutabazi; David Myburgh; Kamie Naidu; Nolene Naidu; Gokul
Nair; Vafa Naraghi; Bridget Nash; Tyrone Negus; Huw Newton-Hill; Buntu Ngcebetsha; Dr. Markus
Oldenburg; Thomas O’Donnell; Dr. Jaynie Padayachee; Poveshen Padayachee; Masimba Paradza;
Dave Pawson; Justin Pead; Nicolette Pekeur; Sirika Pillay; Jacques Plaut; Barry Povey; Andrea Prinsloo;
Joseph Raimondo; Sanya Rajani; Prof. Sergey Rakityansky; Alastair Ramlakan; Dr. Matina J. Rassias;
Dr. Jocelyn Read; Jonathan Reader; Jane Reddick; Dr. Matthew Reece; Razvan Remsing; Laura Richter;
Max Richter; Sean Riddle; Dr. David Roberts; Christopher Roberts; Helen Robertson; Evan Robinson;
Raoul Rontsch; Dr. Andrew Rose; Katie Ross; Jeanne-Marié Roux; Mark Roux; Bianca Ruddy; Nitin
Rughoonauth; Katie Russell; Steven Sam; Dr. Carl Scheffler; Cho Hee Shrader; Nathaniel Schwartz;
Duncan Scott; Helen Seals; Relebohile Sefako; Sandra Serumaga-Zake; Paul Shangase; Cameron Sharp;
Ian Sherratt; Dr. James Short; Roger Sieloff; Brandon Sim; Bonga Skozana; Clare Slotow; Bradley Smith;
Greg Solomon; Nicholas Spaull; Dr. Andrew Stacey; Dr. Jim Stasheff; Mike Stay; Mike Stringer; Masixole
Swartbooi; Tshenolo Tau; Tim Teatro; Ben Thompson; Shen Tian; Xolani Timbile; Nicola du Toit; Robert
Torregrosa; Jimmy Tseng; Pieter Vergeer; Rizmari Versfeld; Mfundo Vezi; Mpilonhle Vilakazi; Mia de
Vos; Helen Waugh; Leandra Webb; Dr. Dawn Webber; Michelle Wen; Neels van der Westhuizen; Dr.
Alexander Wetzler; Dr. Spencer Wheaton; Vivian White; Dr. Gerald Wigger; Harry Wiggins; Heather
Williams; Wendy Williams; Julie Wilson; Timothy Wilson; Andrew Wood; Emma Wormauld; Dr. Sahal
Yacoob; Jean Youssef; Ewald Zietsman; Marina van Zyl

iv


Everything Maths
Mathematics is commonly thought of as being about numbers but mathematics is actually a language!
Mathematics is the language that nature speaks to us in. As we learn to understand and speak this language, we can discover many of nature’s secrets. Just as understanding someone’s language is necessary
to learn more about them, mathematics is required to learn about all aspects of the world – whether it
is physical sciences, life sciences or even finance and economics.
The great writers and poets of the world have the ability to draw on words and put them together in ways
that can tell beautiful or inspiring stories. In a similar way, one can draw on mathematics to explain and
create new things. Many of the modern technologies that have enriched our lives are greatly dependent

on mathematics. DVDs, Google searches, bank cards with PIN numbers are just some examples. And
just as words were not created specifically to tell a story but their existence enabled stories to be told, so
the mathematics used to create these technologies was not developed for its own sake, but was available
to be drawn on when the time for its application was right.
There is in fact not an area of life that is not affected by mathematics. Many of the most sought after
careers depend on the use of mathematics. Civil engineers use mathematics to determine how to best
design new structures; economists use mathematics to describe and predict how the economy will react
to certain changes; investors use mathematics to price certain types of shares or calculate how risky
particular investments are; software developers use mathematics for many of the algorithms (such as
Google searches and data security) that make programmes useful.
But, even in our daily lives mathematics is everywhere – in our use of distance, time and money.
Mathematics is even present in art, design and music as it informs proportions and musical tones. The
greater our ability to understand mathematics, the greater our ability to appreciate beauty and everything
in nature. Far from being just a cold and abstract discipline, mathematics embodies logic, symmetry,
harmony and technological progress. More than any other language, mathematics is everywhere and
universal in its application.
See introductory video by Dr. Mark Horner:

VMiwd at www.everythingmaths.co.za


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CONTENTS

CONTENTS

Contents
1 Algebraic expressions

1

1.1 The real number system . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

1.2 Rational and irrational numbers . . . . . . . . . . . . . . . . . . . . . . .

2

1.3 Rounding off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9

1.4 Estimating surds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.5 Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.6 Factorisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.7 Simplification of fractions . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2 Equations and inequalities
2.1 Solving linear equations

42
. . . . . . . . . . . . . . . . . . . . . . . . . . . 42

2.2 Solving quadratic equations

. . . . . . . . . . . . . . . . . . . . . . . . . 48

2.3 Solving simultaneous equations . . . . . . . . . . . . . . . . . . . . . . . 52
2.4 Word problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
2.5 Literal equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
2.6 Solving linear inequalities
3 Exponents

. . . . . . . . . . . . . . . . . . . . . . . . . . 72
81

3.1 Laws of exponents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.2 Rational exponents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
3.3 Exponential equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

4 Number patterns

96

4.1 Describing sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
4.2 Patterns and conjecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
5 Functions

108

5.1 Functions in the real world . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.2 Linear functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
5.3 Quadratic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.4 Hyperbolic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
5.5 Exponential functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
5.6 Trigonometric functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

xi


CONTENTS

CONTENTS

5.7 Interpretation of graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
6 Finance and growth

192

6.1 Being interested in interest . . . . . . . . . . . . . . . . . . . . . . . . . . 192

6.2 Simple interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
6.3 Compound interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
7 Trigonometry
7.1 Trigonometry is useful

218
. . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

7.2 Similarity of triangles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
7.3 Defining the trigonometric ratios . . . . . . . . . . . . . . . . . . . . . . . 220
7.4 Reciprocal functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
7.5 Special angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
7.6 Solving trigonometric equations . . . . . . . . . . . . . . . . . . . . . . . 228
7.7 Finding an angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
7.8 Two-dimensional problems . . . . . . . . . . . . . . . . . . . . . . . . . . 233
7.9 Defining ratios in the Cartesian plane . . . . . . . . . . . . . . . . . . . . 241
8 Analytical geometry

251

8.1 Drawing figures on the Cartesian plane . . . . . . . . . . . . . . . . . . . 251
8.2 Distance between two points . . . . . . . . . . . . . . . . . . . . . . . . . 252
8.3 Gradient of a line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
8.4 Mid-point of a line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
9 Statistics

284

9.1 Collecting data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
9.2 Measures of central tendency . . . . . . . . . . . . . . . . . . . . . . . . . 288

9.3 Grouping data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
9.4 Measures of dispersion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
9.5 Five number summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
10 Probability

321

10.1 Theoretical probability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
10.2 Relative frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
10.3 Venn diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
10.4 Union and intersection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
10.5 Probability identities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
10.6 Mutually exclusive events . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
10.7 Complementary events . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
11 Euclidean geometry

349

11.1 Quadrilaterals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
xii


CONTENTS

CONTENTS

11.2 The mid-point theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
11.3 Proofs and conjectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383
12 Measurements

394

12.1 Area of a polygon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394
12.2 Right prisms and cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . 397
12.3 Right pyramids, right cones and spheres . . . . . . . . . . . . . . . . . . . 411
12.4 The effect of multiplying a dimension by a factor of k . . . . . . . . . . . . 430
13 Exercise Solutions

439

xiii


CONTENTS

xiv

CONTENTS


Algebraic expressions

1

CHAPTER 1. ALGEBRAIC EXPRESSIONS

1.1

The real number system

EMAA

Real R

Rational Q
Integer Z
Irrational Q�
Whole N0
Natural N

We use the following definitions:
• N: natural numbers are {1; 2; 3; . . .}
• N0 : whole numbers are {0; 1; 2; 3; . . .}
• Z: integers are {. . . ; − 3; − 2; − 1; 0; 1; 2; 3; . . .}
Video: VMabo at www.everythingmaths.co.za

Focus Area: Mathematics

1


1.2

1.2

CHAPTER 1. ALGEBRAIC EXPRESSIONS

Rational and irrational numbers

EMAB

DEFINITION: Rational number
A rational number (Q) is any number which can be written as:
a
b
where a and b are integers and b �= 0.
The following numbers are all rational numbers:
10 21 −1 10 −3
;
;
;
;
1 7 −3 20 6

We see that all numerators and all denominators are integers. This means that all integers
are rational numbers, because they can be written with a denominator of 1.

DEFINITION: Irrational numbers
Irrational numbers (Q� ) are numbers that cannot be written as a fraction with
the numerator and denominator as integers.
Examples of irrational numbers:
√

2;

√

3;

√

3

√
1+ 5
4; π;
2

These are not rational numbers, because either the numerator or the denominator is not
an integer.

2

Focus Area: Mathematics


CHAPTER 1. ALGEBRAIC EXPRESSIONS

1.2

EMAC

Decimal numbers

All integers and fractions with integer numerators and denominators are rational numbers.
You can write any rational number as a decimal number but not all decimal numbers are
rational numbers. These types of decimal numbers are rational numbers:
• Decimal numbers that end (or terminate). For example, the fraction

4
10

can be

written as 0,4.

• Decimal numbers that have a repeating single digit. For example, the fraction 13
can be written as 0,3˙ or as 0,¯
3. The dot and bar notations are equivalent and both
represent recurring 3’s, i.e. 0,3˙ = 0,¯
3 = 0,333 . . ..
• Decimal numbers that have a recurring pattern of multiple digits. For example, the
fraction

2
11

can also be written as 0,18. The bar represents a recurring pattern of 1

and 8’s i.e. 0,18 = 0,181818 . . ..
Notation: You can use a dot or a bar over the repeated numbers to indicate that the
decimal is a recurring decimal. If the bar covers more than one number, then all numbers
beneath the bar are recurring.
If you are asked to identify whether a number is rational or irrational, first write the
number in decimal form. If the number terminates then it is rational. If it goes on forever,
then look for a repeated pattern of digits. If there is no repeated pattern, then the number
is irrational.
When you write irrational numbers in decimal form, you may continue writing them for
many, many decimal places. However, this is not convenient and it is often necessary to
round off.

Focus Area: Mathematics

3


1.2

CHAPTER 1. ALGEBRAIC EXPRESSIONS

Example 1: Rational and irrational numbers
QUESTION
Which of the following are not rational numbers?

1. π = 3,14159265358979323846264338327950288419716939937510 . . .
2. 1,4
3. 1,618033989 . . .
4. 100
5. 1,7373737373 . . .
6. 0,02

SOLUTION
1. Irrational, decimal does not terminate and has no repeated pattern.
2. Rational, decimal terminates.
3. Irrational, decimal does not terminate and has no repeated pattern.
4. Rational, all integers are rational.
5. Rational, decimal has repeated pattern.
6. Rational, decimal has repeated pattern.

4

Focus Area: Mathematics


CHAPTER 1. ALGEBRAIC EXPRESSIONS

Converting terminating decimals into rational
numbers

1.2

EMAD

A decimal number has an integer part and a fractional part. For example, 10,589 has an
integer part of 10 and a fractional part of 0,589 because 10 + 0,589 = 10,589. The fractional part can be written as a rational number, i.e. with a numerator and denominator
that are integers.
Each digit after the decimal point is a fraction with a denominator in increasing powers of 10.
For example,
• 0,1 is

1
10

• 0,01 is

1
100

• 0,001 is

1

1 000

This means that
5
8
9
+
+
10 100 1 000
10 000
500
80
9
=
+
+
+
1 000
1 000 1 000 1 000
10 589
=
1 000

10,589 = 10 +

Converting recurring decimals into rational
numbers

EMAE

When the decimal is a recurring decimal, a bit more work is needed to write the fractional
part of the decimal number as a fraction.

Focus Area: Mathematics

5


1.2

CHAPTER 1. ALGEBRAIC EXPRESSIONS

Example 2: Converting decimal numbers to fractions
QUESTION
Write 0,3˙ in the form

a
(where a and b are integers).
b

SOLUTION
Step 1 : Define an equation
Let x = 0,33333 . . .
Step 2 : Multiply by 10 on both sides
10x = 3,33333 . . .
Step 3 : Subtract the first equation from the second equation
9x = 3
Step 4 : Simplify
x=

6

3
1
=
9
3

Focus Area: Mathematics


CHAPTER 1. ALGEBRAIC EXPRESSIONS

1.2

Example 3: Converting decimal numbers to fractions
QUESTION
Write 5,4˙ 3˙ 2˙ as a rational fraction.

SOLUTION
Step 1 : Define an equation
x = 5,432432432 . . .
Step 2 : Multiply by 1000 on both sides
1 000x = 5 432,432432432 . . .
Step 3 : Subtract the first equation from the second equation
999x = 5 427
Step 4 : Simplify
x=

5 427

201
16
=
=5
999
37
37

In the first example, the decimal was multiplied by 10 and in the second example, the
decimal was multiplied by 1 000. This is because there was only one digit recurring (i.e.
3) in the first example, while there were three digits recurring (i.e. 432) in the second
example.
In general, if you have one digit recurring, then multiply by 10. If you have two digits
recurring, then multiply by 100. If you have three digits recurring, then multiply by 1 000
and so on.

Focus Area: Mathematics

7


1.2

CHAPTER 1. ALGEBRAIC EXPRESSIONS

Not all decimal numbers can be written as rational numbers. Why? Irrational deci√
mal numbers like 2 = 1,4142135 . . . cannot be written with an integer numerator and
denominator, because they do not have a pattern of recurring digits and they do not terminate. However, when possible, you should try to use rational numbers or fractions
instead of decimals.

Exercise 1 - 1

1. State whether the following numbers are rational or irrational. If the
number is rational, state whether it is a natural number, whole number
or an integer:
1
(a) −
3
(b) 0,651268962154862 . . .
√
9
(c)
3
(d) π 2
2. If a is an integer, b is an integer and c is irrational, which of the following
are rational numbers?
5
(a)
6
a
(b)
3
−2
(c)
b
1
(d)
c
3. For which of the following values of a is

a
14

rational or irrational?

(a) 1
(b) −10
√
(c) 2
(d) 2,1
4. Write the following as fractions:
(a) 0,1
(b) 0,12
(c) 0,58
(d) 0,2589
5. Write the following using the recurring decimal notation:
(a) 0,11111111 . . .
8

Focus Area: Mathematics


CHAPTER 1. ALGEBRAIC EXPRESSIONS

1.3

(b) 0,1212121212 . . .
(c) 0,123123123123 . . .
(d) 0,11414541454145 . . .
6. Write the following in decimal form, using the recurring decimal notation:

(a)

2
3

3
11
5
(c) 4
6
1
(d) 2
9
7. Write the following decimals in fractional form:
(b) 1

(a) 0,5˙
(b) 0,63˙
(c) 5,31

More practice

1.3

(1.) 023j

(2.) 00bb

(6.) 00bf

(7.) 00bg

video solutions

(3.) 00bc

or help at www.everythingmaths.co.za

(4.) 00bd

(5.) 00be

Rounding off

EMAF

Rounding off a decimal number to a given number of decimal places is the quickest way
to approximate a number. For example, if you wanted to round off 2,6525272 to three
decimal places, you would:
• count three places after the decimal and place a | between the third and fourth
numbers

• round up the third digit if the fourth digit is greater than or equal to 5
• leave the third digit unchanged if the fourth digit is less than 5
• if the third digit is 9 and needs to be round up, then the 9 becomes a 0 and the
second digit rounded up

Focus Area: Mathematics

9

1.3

CHAPTER 1. ALGEBRAIC EXPRESSIONS

So, since the first digit after the | is a 5, we must round up the digit in the third decimal
place to a 3 and the final answer of 2,6525272 rounded to three decimal places is 2,653.

Example 4: Rounding off
QUESTION
Round off the following numbers to the indicated number of decimal places:
1.

120
99

= 1,1˙ 2˙ to 3 decimal places.

2. π = 3,141592653 . . . to 4 decimal places.
3.

√

3 = 1,7320508 . . . to 4 decimal places.

4. 2,78974526 to 3 decimal places.

SOLUTION

Step 1 : Mark off the required number of decimal places
1.

120
99

= 1,212|121212 . . .

2. π = 3,1415|92653 . . .
3.

√

3 = 1,7320|508 . . .

4. 2,789|74526
Step 2 : Check the next digit to see if you must round up or round down
1. The last digit of

120
99

= 1,212|1212121˙ 2˙ must be rounded

down.
2. The last digit of π = 3,1415|92653 . . . must be rounded up.
3. The last digit of

√

3 = 1,7320|508 . . . must be rounded up.

4. The last digit of 2,789|74526 must be rounded up.
Since this is a 9, we replace it with a 0 and round up
the second last digit.

10

Focus Area: Mathematics