Numbers up to 20
Primary 1 · Mathematics
Numbers up to 20
Lesson 3 of 7
12 min
Let's begin
Gatete helps his aunt at the market in Kigali.
A woman asks for sixteen (16) avocados. Gatete hears sixty (60).
He starts building a huge pile of 60. His aunt laughs and stops him.
Today you will hear the difference, and write it down.
Take 1 bundle of ten sticks again. Add 6 loose sticks.
Start on 10 and count the loose ones: 11, 12, 13, 14, 15, 16.
You have 16, sixteen.
| Sticks | Number | Name |
|---|---|---|
| 1 bundle and 6 | 16 | sixteen |
| 1 bundle and 7 | 17 | seventeen |
| 1 bundle and 8 | 18 | eighteen |
| 1 bundle and 9 | 19 | nineteen |
| 2 bundles | 20 | twenty |
Look at the last row. 20 has no loose sticks at all.
Say sixteen (16). Now say sixty (60). The two words sound close.
Teen means one ten and some ones. It is small. It is under 20.
16 is 1 bundle and 6 loose sticks. You can hold it in two hands.
60 is 6 whole bundles. That is a big pile.
Worked example
write seventeen.
Step 1 Seventeen is 1 ten and 7 ones.
Step 2 Write the tens digit: 1.
Step 3 Write the ones digit beside it: 7.
You have written 17.
Careful! 71 is seven bundles and 1 loose stick. That is not seventeen.
Put 9 loose sticks beside your bundle. That is 19.
Now add 1 more loose stick. You have 10 loose ones.
Tie them together. They become a second bundle.
Two bundles and nothing loose is 20.
So 19 and 1 more make 20.
That is why 20 is written with a 2 and a 0. Two tens, zero ones.
Tip
Teen is a small word for a small number
Hear teen at the end? The number is under 20. Start writing with 1.
Hear ty at the end? The number has many tens. It is much bigger.
Say the number back to the person before you write it.
Count 15 up to 20 with Akili.
Do each one, then tap Show answer to check.
Write eighteen as a number.
Answer: 18. One ten and 8 ones.
What number comes after 19?
Answer: 20. The last loose stick makes a second bundle.
Mutesi has 1 bundle of ten and 7 loose sticks. How many sticks?
Answer: 17. Start on 10, count 11 up to 17.
Read this number out loud: 16.
Answer: sixteen. It is under 20, so it is a teen.
Gatete wrote 60 for sixteen. What should he write?
Answer: 16. Sixteen is 1 ten and 6 ones.
What you learned today
Quick check
A woman asks for sixteen avocados. Which number is that?
