Counting to 20
7 a day ago
🎯 In this topic you will
- Say, read and write numbers and number words up to 20.
- Recognise that teen numbers are made up of one ten and some ones.
🧠 Key Words
- place value cards
- teen numbers
Show Definitions
- place value cards: Learning cards that show tens and ones separately to help students build and understand numbers.
- teen numbers: Numbers from 11 to 19 that are made from one ten and some additional ones.
🔢 Understanding Teen Numbers
In this unit you will look at numbers to 20. These are often called teen numbers because they are made up of a ten and some ones.
🧮 Two Tens Make Twenty
20 is the name for two tens.
❓ EXERCISES
1. Write the missing numbers.
👀 Show answer
The missing numbers are $12$, $13$, $15$, $18$ and $19$.
2. Write the missing numbers.
👀 Show answer
Completed sequences:
$12, 13$
$13, 14, 15$
$17, 18, 19$
$18, 19, 20$
$15, 16$
$16, 17, 18$
$12, 13$
$13, 14, 15$
$17, 18, 19$
$18, 19, 20$
$15, 16$
$16, 17, 18$
3. Which numbers do these place value cards make?
👀 Show answer
$10 + 1 = 11$
$10 + 7 = 17$
$10 + 7 = 17$
4. Which place value cards were used to make each number?
👀 Show answer
$12 = 10 + 2$
$15 = 10 + 5$
$15 = 10 + 5$
🧠 Think like a Mathematician
Investigation: Tomas has place value cards for $1$ to $10$. He says he can make $20$ different numbers with them. Is Tomas correct? How will you find out?
Method:
- Use place value cards from $1$ to $10$.
- Combine the cards in different ways to make as many numbers as possible.
- Write down each number you make so you do not repeat any.
- Count how many different numbers you created.
- Compare your total with Tomas’s claim of $20$ numbers.
Follow-up Questions:
1. How many different numbers can you make?
2. Is Tomas correct?
3. Explain how you know.
Show Answers
- 1: You can make the numbers from $1$ to $20$, which is $20$ different numbers.
- 2: Yes, Tomas is correct.
- 3: By listing every number formed with the place value cards and counting carefully, there are exactly $20$ different numbers.
❓ EXERCISES
5. Say each number. Write the word.
👀 Show answer
$11$ eleven
$12$ twelve
$13$ thirteen
$14$ fourteen
$15$ fifteen
$16$ sixteen
$17$ seventeen
$18$ eighteen
$19$ nineteen
$20$ twenty
$12$ twelve
$13$ thirteen
$14$ fourteen
$15$ fifteen
$16$ sixteen
$17$ seventeen
$18$ eighteen
$19$ nineteen
$20$ twenty
6. Write the missing number words.
👀 Show answer
eleven → $12$ (twelve)
fifteen → $16$ (sixteen)
fourteen → $13$ (thirteen)
fifteen → $16$ (sixteen)
fourteen → $13$ (thirteen)
7. Complete these part-whole diagrams.
👀 Show answer
$14 = 10 + 4$
$11 = 10 + 1$
$11 = 10 + 1$
8. Complete this number puzzle for $19$.
👀 Show answer
$19$ can be shown as:
numeral: $19$
word: nineteen
tens and ones: $10 + 9$
place value: $1$ ten and $9$ ones
numeral: $19$
word: nineteen
tens and ones: $10 + 9$
place value: $1$ ten and $9$ ones
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