In this activity students learn that the code in English for numbers from 13 to 19 the "teen" part of the words means ten.
realise that the meaning of words like sixteen can be decoded by inspection of the word; the six means six and the “teen” means ten.
Large numbers of students fail to realise that “x-teen” in English means “x” ones and one ten. This is a serious impediment to them learning clever mental strategising.
- Ask students to place 10 counters on a frame and 7 on another frame.
Ask how many counters altogether. Watch for the students who count 10, 11, 12, 13, 14, 15, 16, 17. Such students do not understand that the seven in seventeen means seven ones and a ten.
Tell the students the code for “- teen”. It simply a crazy way to spell means ten. Invite them to show explain how they would put out 14, 17 ,19 and 18 on tens frames.
Then address the language issues of the unreliable x-teen coded numbers - fifteen meaning fiveteen, thirteen meaning threeteen.
Address the language issues of the super - unreliable teen words in English. They are twelve which should be twoteen, and eleven which should be oneteen.