Number & place value
Place Value: Tens and Ones
Year 1 · Year 2
- ✓By the end of this lesson students will be able to identify the tens digit and the ones digit in a two-digit number.
- ✓By the end of this lesson students will be able to state the value of each digit in a two-digit number.
- ✓By the end of this lesson students will be able to partition a two-digit number into its tens and ones.
- ✓By the end of this lesson students will be able to combine tens and ones to form a two-digit number.
Key concepts
The 'ones' are the single units in a number. These are the numbers from 0 to 9. In a two-digit number, the ones digit is always the digit on the right.
A 'ten' is a group of 10 single items, or 'ones'. When we count to 10, we have one group of ten. When we count to 20, we have two groups of ten. In a two-digit number, the tens digit is always the digit on the left.
Numbers like 10, 23, 50, and 99 are called two-digit numbers because they are made up of two digits. The first digit (on the left) tells us how many 'tens' there are, and the second digit (on the right) tells us how many 'ones' there are.
Partitioning a number means breaking it apart into its 'tens' and 'ones' to see what it is made of. For example, the number 23 can be partitioned into 2 tens and 3 ones, or 20 + 3.
Key facts to remember
- 1Numbers from 0 to 9 are one-digit numbers.
- 2Numbers from 10 to 99 are two-digit numbers.
- 3A two-digit number always has a tens digit and a ones digit.
- 4The tens digit is on the left, and the ones digit is on the right.
- 5The tens digit tells you how many groups of ten there are.
- 6The ones digit tells you how many single units there are.
- 7Partitioning means breaking a number into its tens and ones.
- 81 ten is the same as 10 ones.
Worked examples
Example 1
How many tens and ones are in the number 47?
Answer
There are 4 tens and 7 ones in the number 47.
The 4 in 47 means 40 (four tens), and the 7 means 7 (seven ones).
Example 2
Partition the number 62.
Answer
62 can be partitioned into 60 + 2, or 6 tens and 2 ones.
You are breaking the number into the value of its parts.
Example 3
What number is made from 3 tens and 5 ones?
Answer
The number is 35.
The tens digit goes first, then the ones digit.
Common mistakes
- ✗Confusing the tens and ones digits (e.g., saying 23 has 3 tens and 2 ones).
- ✗Not understanding that the tens digit represents a value of 'tens' (e.g., thinking 4 tens is 4, not 40).
- ✗Writing the digits in the wrong order when forming a number from tens and ones (e.g., writing 53 instead of 35 for 3 tens and 5 ones).
- ✗Thinking that 'tens' means 'one' and 'ones' means 'ten' when looking at the position.
Exam tips
- ★Always look at the position of the digit: the left digit is tens, the right digit is ones.
- ★Use physical objects like Dienes blocks or counting cubes to help you visualise tens and ones if you are unsure.
- ★When partitioning, always check that your tens and ones add up to the original number.
- ★Read the question carefully to make sure you know if you need to identify, partition, or build a number.
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