Number 10, Tens and Units for Primary 1

Number 10, Tens and Units

Performance Objectives

By the end of the lesson, students should be able to:

1. recognize 10 as a group;
2. place number values appropriately.

Counting to Ten

Numbers help people count how many things there are. When counting, people start from one and go up. After nine, the next number is ten.

Counting to ten means having a collection of ten items. For example, a person has ten fingers on both hands. A person also has ten toes on both feet.

When ten items are put together, they form a group of ten. This group of ten is very important in mathematics.

To recognise 10 as a group, count out ten objects from a larger collection. For example, count ten bottle tops, ten buttons, or ten small balls. When all ten are together, they form one group of ten.

Understanding Tens and Units

Numbers can be shown using ‘Tens’ and ‘Units’. This helps to understand the value of each digit in a number.

A ‘Unit’ is a single item. For example, one bottle top is 1 Unit. Two bottle tops are 2 Units.

A ‘Ten’ is a group of ten single items. When there are ten Units, they can be grouped together to make 1 Ten.

The number 10 is made up of 1 Ten and 0 Units. This means there is one group of ten items and no single items left over.

The Tens and Units Chart

A Tens and Units chart helps to place numbers correctly. It has two columns: one for Tens (T) and one for Units (U).

When writing the number 10 in the chart:

1. The digit ‘1’ goes under the ‘Tens’ column.
2. The digit ‘0’ goes under the ‘Units’ column.

This shows that 10 is 1 Ten and 0 Units.

Numbers from 11 to 20

After 10, numbers continue to grow. These numbers can also be placed in the Tens and Units chart. Numbers from 11 to 19 all have 1 Ten and some Units. The number 20 has 2 Tens and 0 Units.

Placing Numbers in the Tens and Units Chart

To place a number like 11 in the Tens and Units chart:

1. Identify the number of Tens. For 11, there is one group of ten, so it is 1 Ten.
2. Identify the number of Units. For 11, there is one single item left over, so it is 1 Unit.
3. Write ‘1’ under the ‘Tens’ column and ‘1’ under the ‘Units’ column.

This shows that 11 is 1 Ten and 1 Unit.

Here are more examples of how to place numbers from 12 to 20 in the Tens and Units chart:

The numbers from 12 to 20 are:

1. 12: 1 Ten and 2 Units
2. 13: 1 Ten and 3 Units
3. 14: 1 Ten and 4 Units
4. 15: 1 Ten and 5 Units
5. 16: 1 Ten and 6 Units
6. 17: 1 Ten and 7 Units
7. 18: 1 Ten and 8 Units
8. 19: 1 Ten and 9 Units
9. 20: 2 Tens and 0 Units

Reading and Writing Numbers 11 to 20 under Tens and Units

It is important to read and write numbers correctly using the Tens and Units idea. When a number is written in the T U format, it clearly shows its value.

Here is how to read and write numbers from 11 to 20 using the Tens and Units columns:

$$
\begin{array}{|c|c|}
\hline
\textbf{T} & \textbf{U} \\
\hline
1 & 1 \\
\hline
1 & 2 \\
\hline
1 & 3 \\
\hline
1 & 4 \\
\hline
1 & 5 \\
\hline
1 & 6 \\
\hline
1 & 7 \\
\hline
1 & 8 \\
\hline
1 & 9 \\
\hline
2 & 0 \\
\hline
\end{array}
$$

When reading these numbers, say the full number name. For example, ‘1’ in the Tens column and ‘5’ in the Units column is read as “fifteen”. ‘2’ in the Tens column and ‘0’ in the Units column is read as “twenty”.