Year 2: Tens and ones

Key words. A ten is a bundle of ten ones. A one is a single thing.

Method. Count the groups of ten first. Then count the ones left over.

1. Count the tens in 23. Each group of ten is one ten.
   20 is 2 tens
2. Count the ones left over. The ones are what is left after the tens.
   23 − 20 = 3 ones
3. Write the answer.
   2 tens and 3 ones

Check. Put them back together: 20 + 3 = 23. ✓

Watch out. The tens come first when you say the number. 25 is 2 tens and 5 ones.

Method. Count the tens in 70.

1. Look at 70. 70 is 7 tens and 0 ones.
   70 = 7 tens and 0 ones
2. Count the tens. Each ten is counted once.
   7 tens
3. Write the answer.
   7

Check. 7 tens and 0 ones make 70. ✓

Watch out. Read 70 as tens and ones first, then count the tens.

Method. Count the ones in 46.

1. Look at 46. 46 is 4 tens and 6 ones.
   46 = 4 tens and 6 ones
2. Count the ones. Each one is counted once.
   6 ones
3. Write the answer.
   6

Check. 4 tens and 6 ones make 46. ✓

Watch out. Read 46 as tens and ones first, then count the ones.

Method. Start with the tens, then add the ones.

1. Write 5 tens. The tens go on the left.
   5 tens = 50
2. Add 2 ones. The ones go on the right, after the tens.
   50 + 2 = 52
3. Write the number.
   52

Check. Read it back: 52 has 5 tens and 2 ones. ✓

Watch out. The tens digit goes on the left. Write 5 tens and 2 ones as 52.

Method. Start with the tens, then add the ones.

1. Write 1 ten. The tens go on the left.
   1 ten = 10
2. Add 8 ones. The ones go on the right, after the tens.
   10 + 8 = 18
3. Write the number.
   18

Check. Read it back: 18 has 1 ten and 8 ones. ✓

Watch out. The tens digit goes on the left. Write 1 ten and 8 ones as 18.

Key words. The value of a digit is how much it is worth.

Method. The place of a digit tells us what it is worth.

1. Find the tens digit in 73. The tens digit is on the left.
   The tens digit is 7
2. Work out what 7 tens is worth. 7 tens means 7 groups of ten.
   7 tens = 70
3. Write the answer.
   70

Check. 70 + 3 = 73, so the tens and ones make 73. ✓

Watch out. The digit is not always worth what it shows. In 73, the tens digit is worth 70.

Key words. The value of a digit is how much it is worth.

Method. The place of a digit tells us what it is worth.

1. Find the ones digit in 41. The ones digit is on the right.
   The ones digit is 1
2. Work out what 1 one is worth. A digit in the ones place is worth only itself.
   1 one = 1
3. Write the answer.
   1

Check. 40 + 1 = 41, so the tens and ones make 41. ✓

Watch out. The digit is not always worth what it shows. In 41, the ones digit is worth 1.

Key words. A ten is a bundle of ten ones. A one is a single thing.

Method. Count the groups of ten first. Then count the ones left over.

1. Count the tens in 27. Each group of ten is one ten.
   20 is 2 tens
2. Count the ones left over. The ones are what is left after the tens.
   27 − 20 = 7 ones
3. Write the answer.
   2 tens and 7 ones

Check. Put them back together: 20 + 7 = 27. ✓

Watch out. The tens come first when you say the number. 25 is 2 tens and 5 ones.

Method. Most of the numbers have 4 tens. Find the one that does not.

1. Look at the tens of each number. Count the tens in each number.
   43: 4 tens   46: 4 tens   54: 5 tens   49: 4 tens
2. Find the one that is different. 54 has 5 tens. The others have 4 tens.
   54 is different
3. Write the answer.
   54

Check. Check each of the others: they all have 4 tens. ✓

Watch out. Look at the tens digit, not at the ones.

Method. Start with the tens, then add the ones.

1. Write 3 tens. The tens go on the left.
   3 tens = 30
2. Add 4 ones. The ones go on the right, after the tens.
   30 + 4 = 34
3. Write the number.
   34

Check. Read it back: 34 has 3 tens and 4 ones. ✓

Watch out. The tens digit goes on the left. Write 3 tens and 4 ones as 34.

Method. Start with the tens, then add the ones.

1. Write 9 tens. The tens go on the left.
   9 tens = 90
2. Add 0 ones. The ones go on the right, after the tens.
   90 + 0 = 90
3. Write the number.
   90

Check. Read it back: 90 has 9 tens and 0 ones. ✓

Watch out. The tens digit goes on the left. Write 9 tens and 0 ones as 90.

Method. Work out each one, then compare the answers.

1. Work out 40 + 6. 40 is 4 tens. Add 6 ones.
   40 + 6 = 46
2. Work out 4 tens and 6 ones. Four tens is 40, and 6 ones is 6.
   4 tens and 6 ones = 46
3. Compare the answers. They are both 46.
   Yes. Both make 46.

Check. Count in tens to 40, then count on 6 ones. You reach 46. ✓

Watch out. Four tens is the same as 40. The ones do not change.