 # 4.02 Counting back

Lesson

## Ideas

Do you remember how to  count forward  from any number?

### Examples

#### Example 1

Complete the pattern by adding 2 each time.

40,42,44, ⬚, ⬚, ⬚

Worked Solution
Create a strategy

Imagine the numbers are written in the place value table. Add the values in each column.

Apply the idea

The complete pattern is 40,\,42,\,44,\,46,\,48,\,50.

Idea summary

To count forwards we add the numbers.

## Counting back

We can also count backwards from any number. Let's see how we can count backwards by 1,2,5, or 10.

### Examples

#### Example 2

Find the next number in the pattern:

44,\, 39,\,34,\,29,\,24,\,19,\, ⬚

Worked Solution
Create a strategy

We can see how much the numbers are decreasing by counting down on a number line from one of the numbers to the next number in the pattern.

Apply the idea

Count backwards from 44 to 39 to get the difference of 5:

Now we can subtract 5 from the last number in the pattern to get the next number in the pattern:

So the complete pattern is: 44,\, 39,\,34,\,29,\,24,\,19,\, 14.

Idea summary

When we count backwards, our number gets smaller. We can use a number line to help us, by jumping left. Look at how we can count backwards by 2 below.

### Outcomes

#### MA2-5NA

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