2-digit Numbers
Today is a special day—it's Dr. Tariel's birthday! Look at the big cake with all the candles.
Since we have 10 fingers, let's try making groups of ten.
4 tens and 2 ones make the number 42. This is a much quicker way to show a big number! Instead of many single candles, we can just show the number.
Since we have 10 fingers, let's try making groups of ten.
4 tens and 2 ones make the number 42. This is a much quicker way to show a big number! Instead of many single candles, we can just show the number.
Building Numbers
- We can group 10 single cubes (ones) to make 1 ten-stick (ten).
= \(10\) ones \(= 1\) ten =
- To find out how many tens and ones are in a number, we can use a place value chart. Let's look at the number 42:
Tens Ones 4 2 
Definition Digits
The symbols we use to write numbers are called digits. There are ten digits we use to build every number.
| Word | Digit | Cubes |
| zero | 0 | |
| one | 1 |  |
| two | 2 |  |
| three | 3 |  |
| four | 4 |  |
| five | 5 |  |
| six | 6 |  |
| seven | 7 |  |
| eight | 8 |  |
| nine | 9 |  |
Definition Representing 2-Digit Numbers
The place of a digit in a number tells us its value. We can show a number in many ways:
- With digits: $$42$$
- As tens and ones: $$ 4\text{ tens and } 2\text{ ones }$$
- With words:
forty-two - In a place value chart:
Tens Ones 4 2 - With cubes:
Zero is a special digit. It acts as a placeholder to show that a place is empty. For example, in the number 20, the zero shows there are no ones.
On the Number Line
- A number line shows numbers in order, like a long ruler. The numbers get bigger as we move to the right.
- To count big numbers faster, we can take big jumps of 10! This is called counting by tens. We say: "ten, twenty, thirty..."
Definition Number Line
A number line is a line that shows numbers in order from smallest to largest. The distance between each number is always the same.