You can write 11 to 20 and make 10. Now see what teen numbers are made of.
Key idea
Every teen number is ten and some more: 14 is 10 and 4.
Why it works
The 1 in 14 does not mean one thing. It means one whole ten. The 4 means 4 more ones.
Worked example: Ten and seven more
What number is 10 and 7 more?
- Start with a full ten: 10.
- Count on 7: 11, 12, 13, 14, 15, 16, 17.
Answer: 17
Common mistake
Seeing 14 as a 1 and a 4 side by side, as if it were 1 thing and 4 things. The 1 is a whole ten! Show 14 with a full ten frame and 4 more to check.
For grown-ups: Bundle 10 straws with a rubber band. Show teen numbers as one bundle and some loose straws.