1. Counting Two and Three Digit Numbers

Sequencing

This topic explains how to count from 10 to 120. It does so in ranges of numbers, for pacing reasons.

• Counting from 10 to 20
• Counting from 20 to 50
• Counting from 50 to 100
• Counting from 100 to 120

This odule uses the exposure principle to make the learner familiar with the place value concept, which is taught formally at a later time.

Counting from 10 to 20

You have already counted from 1 to 10. Now you will count to 20, which is a larger number than 10. Starting at ten:

Number	How to say the number
10	Ten
11	Eleven
12	Twelve
13	Thirteen
14	Fourteen
15	Fifteen
16	Sixteen
17	Seventeen
18	Eighteen
19	Nineteen
20	Twenty

As with the numbers one to ten, you will need to remember how to say the numbers eleven to twenty. Don't worry if you cannot memorize them right away.

Compared to the numbers 0 to 9, what do you notice about how the numbers 11 to 20 are written? The numbers 11 to 20 contain two numbers put together. Each of these numbers is called a digit. For example:

Ten contains the digits 1 and 0.

Fifteen contains the digits 1 and 5.

Twenty contains the digits 2 and 0.

Why does ten contain two digits, while nine contain only one digit? A digit is not large enough to hold any number larger than nine. For this reason, numbers larger than nine are be written with more than one digit.

Counting from 20 to 50

Number	How to say the number
20	Twenty
21	Twenty one
...	...
49	Forty nine
50	Fifty

Numbers - 48 are not shown.

Problem 1

How many more numbers after 50 can be represented with 2 digits? Think about it. If you are not sure, you will find out in the next section.

Sequencing

This is the first instance where the learner is directly asked to analyze the pattern of how multiple digit numbers are written.

Counting from 50 to 100

Number	How to say the number
50	Fifty
51	Fifty one
...	...
99	Ninety nine
50	One hundred

Numbers 52 - 98 are not shown.

Problem 2

What is similar about the numbers 50 to 100, compared to 20 to 50?

Sequencing

This is the first instance where the learner is directly asked to analyze the pattern of how multiple digit numbers are written.

Count from 100 to 120

Number	How to say the number
100	One hundred
101	One hundred one
...	...
119	One hunderd nineteen
120	One hundred twenty

*Numbers 102 - 118 are not shown.