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Here is part of a number square, look at the coloured numbers, what do you notice?

Each number has two digits. Can you see a pattern?

The numbers get bigger by one from left to right.

Watch: Numbers greater than 9

Example 1

Which numbers are missing from this number line?

Example 2

Which numbers are missing from this number line? What is different about this number line?

Example 3

Here are some socks.

• How many socks have flowers on them?

There are 3 socks with flowers on them.

• How many socks do not have flowers on them?

There are 10 socks which do not have flowers on them.

• How many socks are there altogether?

There are 13 socks altogether.

Showing 15

Here are 15 base ten blocks.

Here are the same 15 base ten blocks arranged as 1 ten (a stick of ten) and 5 ones.

1 ten and 5 ones makes 15.

10 + 5 = 15

15 can also be shown like this using a part whole model. It is split into 1 ten and 5 ones.

Here are two more ways of representing 15 using a ten frame and a bead string.

Can you think of any more ways to show 15?

Activity 2

Order the numbers from smallest at the top, to largest at the bottom.

Activity 3