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Step-by-step practice: Maths · Level 1Chapter 2 · Counting to 20
Level 1 · Chapter 2

Counting to 20

By the end of this chapter you will be able to

  • Count forwards and backwards from 0 to 20
  • Say the number after and before any number up to 20
  • Read and write the numbers 11 to 20
  • Say a number as a ten and some more ones
  • Find a number on a number line and count along it

You should already know

  • Counting to 10 and writing 0 to 10 (Chapter 1)

Where this leads

  • Before, after and between (Level 1, Chapter 3)

Step-by-step practice: maths (Level 1). Small steps, repeated until fluent. Content: Count forwards and backwards to 20, Count from any number to 20, Read and write the numerals 11 to 20, Count sets of up to 20 as tens and ones, Use a number line to find the next or the previous number.

Exercise P  Do you remember?

Non-calculator
1
FCount on from 6. What are the next two numbers?
2
FWhich number comes after 9?
3
FWrite the number 8 as a word.
4
FCount the apples. How many are there?
5
FWhich is more: 3 stars or 6 stars?
2.1

Counting forwards and backwards to 20

Level 1
Count forwards and backwards to 20
Video lesson: Counting forwards and backwards to 20Coming soon

Counting forwards means going up one at a time: 12, 13, 14.

Counting backwards means going down one at a time: 14, 13, 12.

The number after is one more. The number before is one less.

Key ideas

  • Counting forwards: one more each time.
  • Counting backwards: one less each time.
  • The number after 9 is 10.
  • The number before 10 is 9.
Worked example 2.1.1
What number comes after 14?

Method. One more means the next number when we count on.

  1. Start at the number. We begin where we are.
    14
  2. Count on one. Say the number that comes next.
    14 + 1 = 15
  3. Write the answer.
    15

Check. Count back one: 15 take away 1 is 14. It works.

Watch out. One more is the next number, not the same number.

Worked example 2.1.2
What number comes before 15?

Method. One less means the number just before when we count back.

  1. Start at the number. We begin where we are.
    15
  2. Count back one. Say the number that comes just before.
    15 - 1 = 14
  3. Write the answer.
    14

Check. Count on one: 14 add 1 is 15. It works.

Watch out. One less is the number before, not the number after.

Worked example 2.1.3
Fill in the gap: 17, 16, __, 14

Method. Count back one at a time from 17.

  1. Look at the numbers. Each number is one less than the one before.
    17, 16, __, 14
  2. Count back one. After 16 comes 15 when we count back.
    16 - 1 = 15
  3. Write the answer.
    15

Check. Count on from 14: 14, 15, 16, 17. It works.

Watch out. Count back one step at a time.

Watch out

Watch out. When you count backwards, the numbers get smaller. Do not count up by mistake.

Exam tip

Grown-up tip. Count up and down with your child on a stairs, a bus or a wall chart. Start at any number, not always at 1. Ask: “What comes next?”

Exercise 2A  Counting forwards and backwards

Non-calculator
1
FWhat number comes after 11?
2
FWhat number comes before 6?
3
FCount back. Fill in the gap: 5, 4, □, 2
4
FCount on. Fill in the gap: 4, 5, 6, □, 8
5
FWhat number comes after 19?
6
FWhat number comes before 5?
7
FCount back. Fill in the gap: 15, 14, □, 12
8
FCount on. Fill in the gap: 9, 10, 11, □, 13
9
FWhat number comes after 4?
10
FWhat number comes before 19?
11
FCount back. Fill in the gap: 7, 6, □, 4
12
FCount on. Fill in the gap: 8, 9, 10, □, 12
13
FWhat number comes after 1?
14
FWhat number comes before 17?
15
PSCount back. Fill in the gap: 17, 16, □, 14
16
RCount on. Fill in the gap: 10, 11, 12, □, 14
2.2

Numbers 11 to 20

Level 1
Read and write the numbers 11 to 20
Video lesson: Numbers 11 to 20Coming soon

The numbers 11 to 20 are teen numbers. They end with -teen, except 11 and 12.

Each teen number is a ten and some more: 13 is ten and three.

NumeralWord
11eleven
12twelve
13thirteen
14fourteen
15fifteen
16sixteen
17seventeen
18eighteen
19nineteen
20twenty
The numbers 11 to 20 as numerals and as words.

Key ideas

  • Teen numbers are 10 and some more.
  • Eleven and twelve do not end in -teen.
  • The numeral has two digits: 1 for the ten, then the ones.
Worked example 2.2.1
Write the number 13 as a word.

Method. Say the number and find its name.

  1. Look at the numeral. Find the number you need to name.
    13
  2. Say the number name. Each numeral has one number name.
    thirteen
  3. Write the answer.
    thirteen

Check. Count to 13 out loud and check you end on thirteen.

Watch out. Spell the number name carefully. Count the letters you can hear.

Worked example 2.2.2
Write the word “seventeen” as a numeral.

Method. Find the numeral for the number name.

  1. Say the number name. Listen to the word slowly.
    seventeen
  2. Find the number that matches. seventeen is the number 17.
    seventeen = 17
  3. Write the numeral.
    17

Check. Count to 17 and stop on 17.

Watch out. Read the whole number name, not just the first part.

Worked example 2.2.3
Write the number 20 as a word.

Method. Say the number and find its name.

  1. Look at the numeral. Find the number you need to name.
    20
  2. Say the number name. Each numeral has one number name.
    twenty
  3. Write the answer.
    twenty

Check. Count to 20 out loud and check you end on twenty.

Watch out. Spell the number name carefully. Count the letters you can hear.

Watch out

Watch out. Thirteen and thirty look alike when spoken fast. Thirteen is 13 and thirty is 30.

Exam tip

Grown-up tip. Say the teen numbers slowly: fourteen, fifteen, sixteen. Put ten and some more ones with two strips or two cups, so your child can see the ten first.

Exercise 2B  Numbers 11 to 20

Non-calculator
1
FWrite the number 13 as a word.
2
FWrite “seventeen” as a numeral.
3
FWrite the number 13 as a word.
4
FWrite “thirteen” as a numeral.
5
FWrite the number 17 as a word.
6
FWrite “eleven” as a numeral.
7
FWrite the number 12 as a word.
8
FWrite “nineteen” as a numeral.
9
FWrite the number 18 as a word.
10
FWrite “fifteen” as a numeral.
11
FWrite the number 17 as a word.
12
FWrite “twenty” as a numeral.
13
FWrite the number 18 as a word.
14
FWrite “seventeen” as a numeral.
15
PSWrite the number 18 as a word.
16
PSWrite “fourteen” as a numeral.
2.3

Tens and ones

Level 1
Count sets to 20 as tens and ones
Video lesson: Tens and onesComing soon

Ten things make one ten. Put ten things together first.

Then count the ones that are left over.

Here are 13 apples. There is one ten and three ones.

A ten frame is full (10). Three more make 13.

Key ideas

  • Ten is one group of ten.
  • Count the ten first, then count on.
  • A ten and three ones is 13.
Worked example 2.3.1
How many apples are there?

Method. Make a ten first. Then count the ones left over.

  1. Make a ten. Ten apples in one group.
    10
  2. Count the ones left over. These are the extra apples.
    4 ones
  3. Write the answer.
    14

Check. Count all 14 one at a time to check. It matches.

Watch out. Start with the ten, then count on.

Worked example 2.3.2
How many tens and ones are in 18? Write the answer in words.

Method. Find how many complete tens there are, then the ones.

  1. Make a ten. There is one complete ten in 18.
    1 ten
  2. Count the ones. 18 - 10 = 8 ones are left.
    8 ones
  3. Write the answer.
    1 ten and 8 ones

Check. Ten and eight make eighteen.

Watch out. Only one ten fits in 18, so do not say two tens.

Worked example 2.3.3
How many balls are there?

Method. Make a ten first, then count on the rest.

  1. Make a ten. Ten balls in one group.
    10
  2. Count on the rest. There are six more.
    10 + 6
  3. Write the answer.
    16

Check. Count back from 16: you pass one ten and six ones.

Watch out. Count the ten first, not one by one from the start.

Watch out

Watch out. 10 and 1 make 11, not 101. Write one ten and then the ones.

Exam tip

Grown-up tip. Use ten buttons or cubes. Make one group of ten and put the rest beside it. Ask: “How many tens? How many ones? How many altogether?”

Exercise 2C  Tens and ones

Non-calculator
1
FHow many apples are there?
2
FHow many stars are there?
3
FHow many balls are there?
4
PSHow many tens and ones are in 14? Write the answer in words.
5
FHow many apples are there?
6
FHow many stars are there?
7
FHow many balls are there?
8
PSHow many tens and ones are in 19? Write the answer in words.
9
FHow many apples are there?
10
FHow many stars are there?
11
FHow many balls are there?
12
PSHow many tens and ones are in 15? Write the answer in words.
13
FHow many apples are there?
14
FHow many stars are there?
15
RHow many balls are there?
16
PSHow many tens and ones are in 16? Write the answer in words.
2.4

Number lines and number tracks

Level 1
Use a number line to 20, Count on along a number line
Video lesson: Number lines and number tracksComing soon

A number line shows the numbers in order, from left to right.

Each mark is one more than the mark before it. To count on, move right. To count back, move left.

01234567891011121314151617181920
The number line from 0 to 20. The orange dot is 7.

Key ideas

  • A number line goes up in ones from left to right.
  • Count on means move right.
  • Count back means move left.
Worked example 2.4.1
Start at 7. Count on 3. Where do you land?

Method. Start on 7 and count on three steps.

  1. Start on 7. This is where we begin.
    7
  2. Count on three jumps. Each jump moves one number to the right.
    8, 9, 10
  3. Write the answer.
    10

Check. Count back three steps from 10: 9, 8, 7. You are back at 7.

Watch out. Count the jumps, not the numbers you land on.

Worked example 2.4.2
Which number is in the box?
01234567891011?1314151617181920

Method. Look at the numbers next to the box.

  1. Look at the numbers either side. The box is between 11 and 13.
    11 and 13
  2. Count on one. After 11 comes 12.
    11 + 1 = 12
  3. Write the answer.
    12

Check. 12 is one less than 13. It is correct.

Watch out. Read the number line from left to right.

Worked example 2.4.3
Start at 15. What number is one step before it?

Method. One step before means one less.

  1. Start at 15. We begin here.
    15
  2. Count back one step. The number to the left is one less.
    15 - 1 = 14
  3. Write the answer.
    14

Check. Count on one from 14: 15. It works.

Watch out. Before means to the left, so the number gets smaller.

Watch out

Watch out. Count the jumps. If you start on 7 and count on 3, you land on 10, not 11.

Exam tip

Grown-up tip. Draw a number line on paper from 0 to 20. Move a counter along it. Ask your child to say where they land before they move.

Exercise 2D  Number lines and counting on

Non-calculator
1
FLook at the number line. Which number goes in the box?
01?34567891011121314151617181920
2
FLook at the number line. Which number goes in the box?
0123456?891011121314151617181920
3
PSStart at 8 on the number line. Count on 5 steps. Where do you land?
01234567891011121314151617181920
4
FLook at the number line. Which number goes in the box?
0123456789101112131415?17181920
5
FLook at the number line. Which number goes in the box?
0123456789?11121314151617181920
6
PSStart at 4 on the number line. Count on 5 steps. Where do you land?
01234567891011121314151617181920
7
FLook at the number line. Which number goes in the box?
0123?567891011121314151617181920
8
FLook at the number line. Which number goes in the box?
01234?67891011121314151617181920
9
PSStart at 6 on the number line. Count on 6 steps. Where do you land?
01234567891011121314151617181920
10
FLook at the number line. Which number goes in the box?
0123456789?11121314151617181920
11
FLook at the number line. Which number goes in the box?
01234567891011121314?1617181920
12
PSStart at 9 on the number line. Count on 5 steps. Where do you land?
01234567891011121314151617181920
13
FLook at the number line. Which number goes in the box?
01?34567891011121314151617181920
14
FLook at the number line. Which number goes in the box?
0?234567891011121314151617181920
15
PSStart at 8 on the number line. Count on 6 steps. Where do you land?
01234567891011121314151617181920
16
FLook at the number line. Which number goes in the box?
01234567891011121314?1617181920

Chapter summary

SkillMethod
Count forwards and backwardsMove up one for the next number, down one for the number before
Numbers 11 to 20A ten and some more ones. Write the word or the numeral
Tens and onesMake a ten first, then count the ones left over
Number lineCount the jumps. Right is more, left is less

Can you…?

  • I can count forwards and backwards to 20
  • I can say the number after and the number before
  • I can read and write the numbers 11 to 20
  • I can count a set of up to 20 as a ten and some ones
  • I can count on along a number line

Key terms

teen number
a number from 11 to 19, or 20 when we say ten and some more
ten
a group of ten things
ones
the single things left over after the tens
number line
a line with the numbers in order
count on
to keep going up from a number

Exercise 2Z  Check-up

Non-calculator
1
What number comes after 3?
2
What number comes before 11?
3
Count back. Fill in the gap: 8, 7, □, 5
4
Count on. Fill in the gap: 1, 2, 3, □, 5
5
Write the number 20 as a word.
6
Write “twenty” as a numeral.
7
Write the number 14 as a word.
8
How many apples are there?
9
How many stars are there?
10
Look at the number line. Which number goes in the box?
01234567891011?1314151617181920

Total 18 marks. Allow about 18 minutes.

Exercise 2X  Practice test questions

Non-calculator
1
FWhat number comes after 7?[1 mark]
2
FWhat number comes before 15?[1 mark]
3
PSCount back. Fill in the gap: 5, 4, □, 2[1 mark]
4
RCount on. Fill in the gap: 12, 13, 14, □, 16[1 mark]
5
FWrite the number 12 as a word.[2 marks]
6
PSWrite “eleven” as a numeral.[2 marks]
7
PSWrite the number 12 as a word.[2 marks]
8
RHow many apples are there?[2 marks]
9
RHow many stars are there?[3 marks]
10
FLook at the number line. Which number goes in the box?[3 marks]
012?4567891011121314151617181920
← Chapter 1: Counting to 10Chapter 3: Before, after and between →

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