Year 7 Interactive Maths - Second Edition

Whole Numbers

The Number System

We use the Hindu-Arabic system which uses the following ten digits:

0   1   2   3   4   5   6   7   8   9

If a number is greater than 9, we represent it by using two or more digits which are placed together horizontally.

Our number system uses a place system.  This means that the place value of a digit in a number depends on the column in which the digit is placed.

E.g.  The number 35 is formed by using the digits 3 and 5 representing 3 tens and 5 units respectively.

The number system we use is a 'base 10' system.  Therefore, each 'column' in the place value system is a power of 10 as shown below.

This suggests that 685 can be written as follows:

So, 685 is the number six hundred and eighty-five.

 

Likewise, 3849 can be represented as follows:

So, 3849 is the number three thousand, eight hundred and forty-nine.

Example 1

Write 74 in words.

Solution:

74 is the number seventy-four.

Example 2

Write 3 128 659 in words.

Solution:

3 128 659 is the number three million, one hundred and twenty-eight thousand, six hundred and fifty-nine.

Example 3

What number does the digit 8 in the following numbers represent?

a.  38
b.  82
c.  384
d.  867
e.  8001
f.  186 345
g.  9 351 278
h.  369 481
i.   45 986
j.   283 000

Solution:

The number represented by the digit 8 is:

a.  8
b.  80
c.  80
d.  800
e.  8000
f.   80 000
g.  8
h.  80
i.   80
j.   80 000

Key Terms

place system, place value, base 10 number system, numbers as words, digits