What is this skill?
Teen numbers are 11 to 19, and this skill is about seeing each one as a ten and some more ones. Fourteen is ten and four more; seventeen is ten and seven more. Children practice this with ten frames, bundles of ten sticks, or blocks, and by connecting the pictures to equations such as 10 + 4 = 14.
The written numerals help once children understand them: the 1 in 14 stands for one ten, and the 4 stands for four ones. That is a big idea, because it means the same digit can have different values depending on where it is written.
Why it matters
This is the first step into place value, the idea that our number system is built on tens. Everything from reading 47 as four tens and seven ones in first grade, to adding with regrouping in second grade, to understanding decimals in fourth grade, grows from this skill.
It also helps with adding and subtracting. A child who knows that 10 + 6 = 16 without counting can use ten as a stepping stone: to work out 9 + 6, make 10 and then add the rest.
The English names make this harder than it needs to be. Eleven and twelve do not sound like "ten and one" or "ten and two," and words like thirteen and fifteen hide the three and five. Seeing the ten and the extra ones, rather than relying on the names, gives children a picture that the words alone do not provide.
Common mistakes
- Writing teen numbers backwards, like 41 for fourteen, because we say the "four" first. Point out that the ten is always written first, on the left.
- Thinking the 1 in 15 means one thing rather than one ten. Building the number with a bundle of ten and five single sticks helps make the value of the 1 visible.
- Confusing teen numbers with the matching tens, such as sixteen and sixty. Saying them slowly and clearly together, and showing both with objects, helps.
How to help at home
- Make bundles of ten using craft sticks, straws or pencils and a rubber band. Build teen numbers with one bundle and some single sticks.
- Use two hands of ten fingers: you hold up ten, your child holds up the extra ones, and together you say the number.
- Write a teen number and ask your child to show it with an egg carton filled to ten plus extra objects outside it.
- Play "ten and how many more?": say a teen number and ask how many more than ten it is. Then flip it: "Ten and three more is what number?"
Worked examples
These are real questions from the Tutorsaurus teen numbers practice, with the answers worked out.
Example 1
10 and 9 more is…
Choices: 18, 16, 17, 19
Answer: 19. Ten and 9 ones make 19.
Example 2
10 and 7 more is…
Choices: 15, 20, 17, 18
Answer: 17. Ten and 7 ones make 17.
Example 3
10 and 1 more is…
Choices: 10, 11, 14, 13
Answer: 11. Ten and 1 ones make 11.