 # 3.02 Counting on

Lesson

## Ideas

Do you remember how to  count forward  by 10?

### Examples

#### Example 1

What is 20 + 10?

Worked Solution
Create a strategy

Put the numbers in a place value table and add the values in each column.

Apply the idea

Put the numbers in a place value table and add the numbers in each column:

Add the smallest place value first. So 0 + 0 makes 0.

Then add the next place value. 2 + 1 would make 3.

So 20 + 10 = 30.

Idea summary

To add numbers we can use a place value table.

## Count on by 1 and 2

Let's see how we can count on by 1, and then 2. What patterns do we make?

### Examples

#### Example 2

Write the next number in the pattern:

1,\,3,\,5,\,7,\,9,\, 11,\,⬚

Worked Solution
Create a strategy

Get the next value by counting on to complete the pattern.

Apply the idea

Count on from 1 to 3 to get the increase of 2 as shown in the number line.

So to get the next number in the pattern, we need to count on from 11 by 2. We can add them together using a place value table.

The next number in the pattern is 13:1,\,3,\,5,\,7,\,9,\, 11,\,13

Idea summary

When we count on by 1, and then 2, we can make patterns of odd or even numbers.

## Count on by 5 and 10

What patterns do you see if we count by 5, or 10?

### Examples

#### Example 3

Write the next number in the pattern:

3,\,8,\,13,\,18,\,23,\, 28,\, ⬚

Worked Solution
Create a strategy

Get the next values by counting on to complete the pattern.

Apply the idea

Count on from 3 to 8 to get the increase of 5. As shown in the number line below.

So to get the next number in the pattern, we need to count on from 28 by 5. We can add them together using a place value table.

The next number in the pattern is 33:3,\,8,\,13,\,18,\,23,\, 28,\, 33

Idea summary

When we count on, we can use the pattern to help us work out the next number.

### Outcomes

#### MA2-5NA

uses mental and written strategies for addition and subtraction involving two-, three-, four and five-digit numbers

#### MA2-8NA

generalises properties of odd and even numbers, generates number patterns, and completes simple number sentences by calculating missing values