3
1.1 Understanding Whole Numbers
Introduction
Counting Numbers
or
Natural Numbers
0
1
2
3
4
Whole numbers are simply the numbers 0, 1, 2, 3, 4.... They include all counting numbers, also
known as natural numbers or positive integers (1, 2, 3, 4...), and zero (0).
All whole numbers are integers. However, whole numbers and integers are not the same because
integers include counting numbers (positive integers) and their negatives (negative integers).
Whole Numbers
Natural Numbers
(Positive Integers)
Whole Numbers
Integers
Zero
Negative Integers
Place Value of Whole Numbers
All numbers can be made up using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. Numbers may consist of
one or more digits. When a number is written using the above digits, it is said to be in standard form.
For example, 7, 85, and 2,349 are examples of numbers in their standard form where 7 is a single(one) digit number, 85 is a two-digit number, and 2,349 is a four-digit number.
The position of each digit in a whole number determines the place value for the digit.
Exhibit 1.1-a illustrates the place value of the ten digits in
the whole number, 3,867,254,129. In this whole number,
4 occupies the 'thousands' place value and represents
4 thousand, or 4,000; whereas 7 occupies the 'millions'
place value and represents 7 million, or 7,000,000.
3,867,254,129
ones
tens
hundreds
thousands
ten thousands
hundred thousands
millions
ten millions
hundred millions
billions
We read and write numbers from the left to the right. A
comma (or alternatively, a space) separates every three
digits into groups, starting from the place value for
'ones', thereby making it easier to read a whole number.
The place value of 'ones' is 100 ( = 1) and each position
has a value 10 times the place value to its right, as
shown in Table 1.1.
Table 1.1
Exhibit 1.1-a Place Value of a Ten-Digit Whole Number
Place Value Chart of Whole Numbers
109
108
1,000,000,000 100,000,000
Billions
Hundred
millions
107
106
105
104
103
102
101
100
10,000,000
1,000,000
100,000
10,000
1,000
100
10
1
Ten
millions
Millions
Hundred
thousands
Tens
Ones
Ten
Thousands Hundreds
thousands
A number in standard form is separated into groups of three digits using commas. The vertical red
lines in Table 1.1 denote the positions of the commas that separate the groups of three numbers,
starting from the place value for 'ones'.
1.1 Understanding Whole Numbers
4
For example, the 10-digit whole number in Exhibit 1.1-a, written as 3,867,254,129, is represented in
its standard form for writing numbers.
3
8
6
7
2
5
4
1
2
9
Numbers can be written in standard form and in expanded form using figures, or in word form.
For example, number 3,867,254,129 in standard form can be written in expanded form, as follows:
3,000,000,000 + 800,000,000 + 60,000,000 + 7,000,000 + 200,000
+ 50,000 + 4,000 + 100 + 20 + 9
Or
3 billion + 800 million + 60 million + 7 million + 200 thousand
+ 50 thousand + 4 thousand + 1 hundred + 2 tens + 9 ones
This can also be written in word form, as follows:
Three billion, eight hundred sixty-seven million, two hundred fifty-four thousand, one hundred twenty-nine.
Example 1.1-a
Identifying the Place Value of a Digit and the Amount it Represents
What is the place value of the digit 5 in each of the following numbers and what amount does it represent?
(i) $2,543
(ii) $75,342
(iii) $6,521,890
(iv) $915,203,847
Solution
(i) $2,543
(ii) $75,342
(iii) $6,521,890
(iv) $915,203,847
Place value of the digit 5:
Hundreds
Thousands
Hundred Thousands
Millions
$500
$5,000
$500,000
$5,000,000
Amount it represents:
Example 1.1-b
Identifying the Digit of a Number Given its Place Value
In the number 5,320,948 identify the digit that occupies the following place values:
(i)
Hundred thousands
(iv) Tens
Solution
(i)
5,320,948
(ii)
Ten thousands
(iii) Thousands
(v)
Hundreds
(vi) Millions
(ii)
5, 320,948
(iii) 5,320,948
Hundred thousands
(iv) 5,320,948
(v)
Tens
Example 1.1-c
Thousands
Ten thousands
5,320,948
(vi) 5,320,948
Hundreds
Millions
Writing Numbers in Expanded Form
Write the following numbers in expanded form:
Solution
(i)
698
(ii)
8,564
(iii)
49,005
(iv)
521,076
(v)
9,865,323
(vi)
43,583,621
(i)
698
600 + 90 + 8
(ii)
8,564
8,000 + 500 + 60 + 4
Chapter 1 | Whole Numbers
5
(iii) 49,005
40,000 + 9,000 + 5
(iv) 521,076
500,000 + 20,000 + 1,000 + 70 + 6
(v)
9,865,323
9,000,000 + 800,000 + 60,000 + 5,000 + 300 + 20 + 3
(vi) 43,583,621
40,000,000 + 3,000,000 + 500,000 + 80,000 + 3,000 + 600 + 20 + 1
Reading and Writing Whole Numbers
To make it easier to read and write numbers, any number larger than three digits is separated into smaller
groups of three digits, starting from the last digit of the number. Each group of these three digits has a name.
■■ The first group of 3 digits on the right is the “Units” group.
■■ The second group from the right is the “Thousands” group.
■■ The third group from the right is the “Millions” group.
■■ The fourth group from the right is the “Billions” group.
■■ The fifth group from the right is the “Trillions” group and so on, as shown in the following chart.
Ones
Tens
Units
Hundreds
Ones
Tens
Hundreds
Thousands
Ones
Tens
Hundreds
Millions
Ones
Tens
Hundreds
Billions
Ones
Tens
Trillions
Hundreds
Follow these steps to write large numbers in word form:
Step 1:
Start from the group furthest to the left and write the number formed by the digits in that
group, followed by the name of the group.
Step 2:
Moving to the next group (to the right), write the numbers formed by this next group,
followed by its name. Continue to do this for each of the groups.
Step 3:
For the last group (i.e., the group furthest to the right), write the numbers formed by the
group; however, for this group, do not write the name of it.
Note: When a group contains all zeros, that group is never read or written.
Also, commas and hyphens are used when expressing numbers in word form.
■■ Commas (,) are used between the groups to separate them.
■■ Hyphens (-) are used to express the two digit numbers in each group;
i.e., 21 to 29, 31 to 39, 41 to 49,…91 to 99.
For example, 2,835,197,000,642 expressed in word form using the above rules would be as follows:
Hundreds
Tens
Ones
Hundreds
Tens
Ones
Hundreds
Tens
Ones
Units
Ones
Thousands
Tens
Millions
Hundreds
Billions
Ones
Trillions
Tens
continued
Hundreds
Solution
2
8
3
5
1
9
7
0
0
0
6
4
2
Two trillion,
eight hundred one hundred
thirty-five ninety-seven
billion,
million,
six hundred
forty-two
1.1 Understanding Whole Numbers
6
The word ‘and’ does not
appear in the word form of
whole numbers.
When writing the numbers in word form, the names of the groups remain in their singular form,
irrespective of the number preceeding; i.e., hundred, thousand, million, billion, trillion, etc.
For example:
•
Eight hundred thirty-five billion.
•
One hundred ninety-seven million.
Exhibit 1.1-b Sample of a cheque showing a number expressed in its standard form and word form.
Example 1.1-d
Writing Numbers in Word Form Given their Standard Form
Write the following numbers in word form:
Solution
(i)
743
(ii)
5,006
(iii)
15,017
(iv)
800,629
(v)
6,783,251
(vi)
52,630,042
(i)
743
Seven hundred forty-three.
(ii)
5,006
Five thousand, six.
(iii) 15,017
Fifteen thousand, seventeen.
(iv) 800,629
Eight hundred thousand, six hundred twenty-nine.
(v)
Six million, seven hundred eighty-three thousand, two hundred fifty-one.
6,783,251
(vi) 52,630,042
Example 1.1-e
Fifty-two million, six hundred thirty thousand, forty-two.
Writing Numbers In Standard Form Given their Word Form
Write the following in standard form:
(i)
Two hundred five
(ii)
Six thousand, four
(iii)
Thirty-five thousand, eight hundred twenty-five
(iv)
Eight hundred thousand, five
(v)
Two million, three hundred forty-two thousand, six hundred seventeen
(vi)
Half of a million
(vii) Three-quarters of a billion
Chapter 1 | Whole Numbers
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Solution
(i)
Two hundred five
205
(ii)
Six thousand, four
6,004
(iii) Thirty-five thousand, eight hundred twenty-five
35,825
(iv) Eight hundred thousand, five
800,005
(v)
Two million, three hundred forty-two
thousand, six hundred seventeen
2,342,617
(vi) Half of a million
1
2 × 1,000,000 = 500,000
(vii) Three-quarters of a billion
3 × 1,000,000,000 = 750,000,000
4
Number Line
Whole numbers can be represented graphically as a point on a horizontal line, called the number line, as
shown below.
The arrowhead at the end shows that the line continues indifinitely in that direction.
0
−3 −2 −1
Negative
Integers
1
2
3
Positive
Integers
Zero is neither positive
nor negative.
0
1
2
3
4
6
5
7
The smallest whole number is zero (0). It is not possible to find the largest whole number because for
any given number, there will always be another number greater than that number.
Writing numbers on a number line helps in comparing and identifying numbers that are smaller or
larger than other numbers. Numbers that lie to the left of a number on the number line are smaller
than the numbers that lie to the right of that number, and vice versa.
For example,
•
6 is greater than 2 (or 2 is less than 6).
•
5 is less than 7 (or 7 is greater than 5).
0 1 2 3 4 5 6 7 8
0 1 2 3 4 5 6 7 8
The signs used to show the relative position of two numbers (or quantities) are:
The signs < and > always point
towards the smaller number.
(i) ‘ > ’ read as “greater than”, meaning that the number on the left of the sign has a value greater
than that on the right.
For example, “6 is greater than 2” is written as 6 > 2.
This is the same as “2 is less than 6” and written as 2 < 6.
(ii) ‘ < ’ read as “less than”, meaning that the number on the left of the sign has a value less than
that on the right.
For example, “5 is less than 7” is written as 5 < 7.
This is the same as “7 is greater than 5” and written as 7 > 5.
Example 1.1-f
Graphing Numbers on a Number Line and Using Signs to Show the Relative Positions of the Numbers
For each of the following, graph the numbers on a number line and place the correct sign,
in the spaces between the numbers:
(i)
7
11
5
(ii)
11
12
(iii)
3
5
12
(iv)
12
7
<
or
>
,
5
3
1.1 Understanding Whole Numbers
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Solution
(i)
(ii)
7 < 11 > 5
5
7
5
0
11 12
0
(iii) 3 < 5 < 12
3
(iv) 12 > 7 > 3
5
12
3
0
Example 1.1-g
11 < 12 > 5
11
7
12
0
Writing a Statement to Represent “>” or “<”
Write statements using the words “greater than” or “less than” for the following expressions:
Solution
(i)
24 > 22
(i)
24 > 22
(ii)
36 < 39
(iii)
9>0
(iv)
0<5
24 is greater than 22 or 22 is less than 24.
(ii)
36 < 39 36 is less than 39 or 39 is greater than 36.
(iii) 9 > 0
9 is greater than 0 or 0 is less than 9.
(iv) 0 < 5 0 is less than 5 or 5 is greater than 0.
Rounding Whole Numbers
Rounding numbers makes them easier to work with and easier to remember. Rounding changes
some of the digits in a number but keeps its value close to the original. It is used in reporting large
quantities or values that change often, such as population, income, expenses, etc.
For example, the population of Canada is approximately 33 million or Henry’s car expense for this
month is approximately $700.
The rounding of numbers also makes arithmetic operations faster and easier, especially when
determining the exact answer is not required.
For example, if you are required to estimate the area of a rectangular plot of land that measures 114 m
by 97 m, you would have to multiply 114 × 97, which would result in 11,058 m2. However, rounding
the measurements to the nearest ten can provide a quick estimate.
For example,
•
Rounding 114 m to the nearest ten is 110 m.
•
Rounding 97 m to the nearest ten is 100 m.
110
114
90
This would result in an estimated area of 110 × 100 = 11,000 m2.
97
120
114 is closer to 110 than 120.
Therefore, round down to 110.
100
97 is closer to 100 than 90.
Therefore, round up to 100.
­­­Rounding Whole Numbers to the Nearest Ten, Hundred, Thousand, etc.
Rounding whole numbers refers to changing the value of the whole number to the nearest ten,
hundred, thousand, etc. It is also referred to as rounding whole numbers to multiples of 10, 100,
1,000, etc.
Chapter 1 | Whole Numbers
9
For example,
•
Rounding a whole number to the nearest ten is the same as rounding it to a multiple of 10.
•
Rounding a whole number to the nearest hundred is the same as rounding it to a multiple of 100.
•
Rounding an amount to the nearest $10 refers to rounding the amount to a multiple of $10.
Follow these steps to round whole numbers:
Step 1:
Identify the digit to be rounded (this is the place value for which the rounding is required).
Step 2:
If the digit to the immediate right of the required rounding digit is less than 5 (0, 1, 2, 3, 4),
do not change the value of the rounding digit.
If the digit to the immediate right of the required rounding digit is 5 or greater than 5 (5, 6,
7, 8, 9), increase the value of the rounding digit by one (round up by one number).
Step 3:
Example 1.1-h
After Step 2, change the value of all digits that are to the right of the rounding digit to 0.
Rounding Numbers Using Number Line (Visual Method)
Round the following numbers to the indicated place value using a number line:
Solution
(i)
624 to the nearest ten (multiple of 10).
(ii)
150 to the nearest hundred (multiple of 100).
(iii)
1,962 to the nearest hundred (multiple of 100).
We can visualize these numbers on a number line to determine the nearest number:
(i)
624 to the nearest ten (multiple of 10).
620
624
630
0
624 is closer to 620 than to 630.
Therefore, 624 rounded to the nearest ten is 620.
(ii)
150 to the nearest hundred (multiple of 100).
100
150
200
0
150 is exactly between 100 and 200. By convention, if a number is exactly in the middle, we
round it up.
Therefore, 150 rounded to the nearest hundred is 200.
(iii) 1,962 to the nearest hundred (multiple of 100).
1,900
1,962
2,000
0
1,962 is closer to 2,000 than to 1,900.
Therefore, 1,962 rounded to the nearest hundred is 2,000.
Example 1.1-i
Rounding to Indicated Place Values
Round the following to the indicated place values:
(i)
$568 to the nearest $10.
(ii)
$795 to the nearest $10.
(iii)
$5,643 to the nearest $100.
(iv)
$19,958 to the nearest $100.
1.1 Understanding Whole Numbers
10
Solution
(i)
Rounding $568 to the nearest $10.
Identify the rounding digit in the tens place: 568 (6 is the digit in the tens place).
The digit to the immediate right of the rounding digit is 8, which is greater than 5;
therefore, increase the value of the rounding digit by one, from 6 to 7, and change the value
of the digits that are to the right of the rounding digit to 0, which will result in 570.
568
560
565
570
Therefore, $568 rounded to the nearest $10 (or multiple of 10) is $570.
(ii)
Rounding $795 to the nearest $10.
Identify the rounding digit in the tens place: 795 (9 is the digit in the tens place).
The digit to the immediate right of the rounding digit is 5; therefore, increase the value
of the rounding digit by one, from 9 to 10. This is done by replacing the rounding digit
9 with 0, and increasing the next digit to its left by one, from 7 to 8. Change the value
of the digits that are to the right of the rounding digit to 0, which will result in 800.
795
790
800
Therefore, $795 rounded to the nearest $10 (or multiple of 10) is $800.
(iii) Rounding $5,643 to the nearest $100.
Identify the rounding digit in the hundreds place: 5,643 (6 is the digit in the hundreds place).
The digit to the immediate right of the rounding digit is 4, which is less than 5;
therefore, do not change the value of the rounding digit, but change the value of the
digits that are to the right of the rounding digit to 0, which will result in 5,600.
5,643
5,600
5,650
5,700
Therefore, $5,643 rounded to the nearest $100 (or multiple of $100) is $5,600.
(iv) Rounding $19,958 to the nearest $100.
Identify the rounding digit in the hundreds place: 19,958 (9 is the digit in the hundreds place).
19,958
19,900
19,950
20,000
The digit to the immediate right of the rounding digit is 5; therefore, increase the value of the
rounding digit by one, from 9 to 10. This is done by replacing the rounding digit 9 with 0 and
increasing the next digit to its left by one. In this case it is 9, so increase again from 9 to 10.
Replace that digit 9 with 0 and increase the number to its left by one, from 1 to 2. Change the
value of the digits that are to the right of the rounding digit to 0, which will result in 20,000.
Therefore, $19,958 rounded to the nearest $100 (or multiple of $100) is $20,000.
1.1 Exercises
Answers to odd-numbered problems are available at the end of the textbook.
For Problems 1 to 4, write (i) the place value of the underlined digit and (ii) the value it represents.
1. a. 4,792
b. 5,352
c. 45,721
2. a. 7, 628
b. 4,687
c. 94,083
3. a. 319,526
b. 7,825,500
c. 16,702,555
4. a. 204,095
b. 35,217,123
c. 4,385,207
For Problems 5 to 10, write the numbers in their (i) expanded form and (ii) word form.
5. a. 407
b. 2,056
6.
a. 860
b. 7,805
7. a. 29,186
b. 464,448
8. a. 94,975
b. 684,137
9.
a. 2,604,325
b. 15,300,604
10. a. 9,084,351
b. 23,006,045
For Problems 11 to 16, write the numbers in their (i) standard form and (ii) word form.
11. a. 600 + 70 + 9
b. 3,000 + 100 + 40 + 7
12.
a. 400 + 50 + 6
b. 1,000 + 900 + 30 + 2
13. a. 2,000 + 600 + 5
b. 9,000 + 20 + 4
14.
a. 5,000 + 300+1
b. 7,000 + 80 + 8
15. a. 40,000 + 900 + 90
b. 10,000 + 50 + 3
16.
a. 60,000 + 700 + 80
b. 20,000 + 100 + 4
For Problems 17 to 24, write the numbers in their (i) standard form and (ii) expanded form.
17. a. Five hundred seventy
b. Eight hundred three
Chapter 1 | Whole Numbers
18. a. One thousand five
b. Seven thousand twenty
11
19. a. Eighty thousand, six hundred thirty
b. Seventy-five thousand, twenty-five
20. a. Sixty-five thousand, two hundred forty-four
b. Eight hundred thirty-three thousand, six hundred forty-one
21. a. Twelve million, four hundred fifty-two thousand, eight hundred thirty-two
b. Thirty-two million, six hundred eighty-four thousand, two hundred fifty-six
22. a. Two billion, one thousand
b. One billion, twenty-five thousand
23. a. One-eighth of a million
b. Three-quarters of a million
24. a. Half of a billion
b. One-tenth of a billion
For Problems 25 and 26, plot the numbers on a number line.
25. a. 14, 19, 15, 7
b. 12, 8, 17, 5
26. a. 18, 9, 6, 11
b. 4, 10, 7, 16
For Problems 27 and 28, place the correct sign ‘<’ or ‘>’ in the space between the numbers.
27. a. 7
15
28. a. 12
17
b. 19
b. 8
14
5
c. 0
5
c. 17
d. 19
0
0
d. 0
8
For Problems 29 and 30, express the relationship between numbers using the statement (i) “less than” and (ii) “greater than”.
29. a. 6 < 9
b. 18 > 11
c. 5 < 11
d. 11 > 0
30. a. 4 < 7
b. 16 > 7
c. 10 < 16
d. 0 < 4
For Problems 31 to 34, arrange the numbers in order from smallest to largest.
31. a. 87; 108; 99; 103; 96
b. 159; 141; 108; 139; 167
32. a. 58; 129; 147; 49; 68
b. 836; 820; 805; 873; 875
33. a. 2,067; 2,040; 2,638; 2,533
b. 79,487; 79,534; 79,468; 78,812
34. a. 2,668; 2,630; 2,579; 2,759
b. 68,336; 69,999; 69,067; 68,942
For Problems 35 and 36, create the (i) smallest and (ii) largest possible numbers using all the given digits.
35. a. 9, 2, 5
b. 7, 9, 1, 8
c. 3, 5, 4, 8
36. a. 6, 1, 7
b. 9, 4, 8, 5
c. 4, 7, 2, 6, 5
For Problems 37 and 38, round the numbers to (i) nearest ten, (ii) nearest hundred, and (iii) nearest thousand.
37.
Number
a.
425
b.
1,645
c.
53,562
d.
235,358
Nearest
Ten
Nearest
Hundred
Nearest
Thousand
1.1 Understanding Whole Numbers
12
38.
Nearest
Ten
Number
a.
Nearest
Hundred
Nearest
Thousand
895
b.
9,157
c.
25,972
d.
139,835
For Problems 39 and 40, round the numbers to (i) nearest ten thousand, (ii) nearest hundred thousand, and (iii) nearest million.
39.
Number
a.
875,555
b.
1,656,565
c.
3,368,850
d.
4,568,310
40.
Number
a.
759,850
b.
3,254,599
c.
7,555,450
d.
2,959,680
Nearest
Ten Thousand
Nearest
Hundred Thousand
Nearest
Million
Nearest
Ten Thousand
Nearest
Hundred Thousand
Nearest
Million
1.2 Arithmetic Operations with Whole Numbers
Addition of Whole Numbers
Addition can be done in any
order and the sum will be
the same.
A+B=B+A
For example,
9 + 5 = 14, and 5 + 9 = 14
This is known as the
commutative property of
addition.
Addition of whole numbers refers to combining two or more (finding the total or sum of) numbers
and finding the answer.
When numbers are added, the numbers added are called addend. The result or answer is called the
total, sum, or amount.
The symbol ‘+’ denotes addition.
For example, 9 + 5 refers to adding 9 and 5.
9
Plus sign
+ 5
14
Addend
Total, sum, or amount
Follow these steps to add one number to another number:
Example 1.2-a
Step 1:
Start by writing the numbers one under the other by aligning the place values (ones, tens,
hundreds, etc.) of these numbers and drawing a horizontal line.
Step 2:
Starting with the ones place value, add all the numbers in the ‘ones’ column. If their total
is less than 10, write the total under the horizontal line. If the total is 10 or more, write the
‘ones’ digit of the total under the horizontal line and write the tens digit above the tens
column. This is called ‘carrying’.
Step 3:
Add the numbers in the tens column followed by the hundreds column, etc., by following
the same procedure for each column.
Adding Whole Numbers
Perform the following additions:
(i)
Chapter 1 | Whole Numbers
3,514 + 245
(ii)
8,578 + 3,982 + 564 + 92