I have come across a number of factors that stand in the way of children understanding our number system. One issue is our language (English, if you haven’t noticed yet), and the way we name numbers. Number names aren’t always logical, and can confuse many of our students. Here are some ideas to mitigate language confusion for those struggling to gain number sense and understand our base 10 system, and to enrich understanding for those who “get it,” but can go deeper.
You will likely have come across the fact that in some language families, such as Chinese and Algonquin, number names actually describe the number structure. Take 24 for example. In English it’s “twenty-four,” whereas these other languages say the equivalent of two-tens-and-four. The unitizing of TENS and the addition of ONES are plainly obvious. The very act of learning number words in these languages teaches the number system.
So, in my class, I make the language we use equally explicit. Here is how.
What is 10? In our system, TEN can be a series of or a pile of single ONES. It can also be a single unit that contains 10 ONES. I make the comparison between 10 pennies and a dime, or eating 10 cookies one at a time versus buying 1 bag of 10 cookies. I talk about having 10 birthdays and being 10 years old. This comes up when we are practicing skip counting, growing patterns, and working with money. Students must have a strong sense of TENness before they can understand base 10 and place value.
After 10, we have 20. While not as explicit as in Chinese, the word TWENTY has clues to how many it stands for. TW- comes from TWO. -TY implies ten. So TWENTY is Two TEN. We build on that. As a class, we look at THIRTY to see if there are any clues to how many it is. Then we look at FORTY, FIFTY, etc. Don’t forget to look at the words in relation to the numerals. To make it even clearer, I will list all the 10s that make the number in a column, and add them together in a sum below, counting the number of TENS, One TEN, Two TENS, Three TENS, that makes THIREE-TENS, or 30.
Now do 10s with 1s. Twenty-One means Two TENS and One ONE. Fifty-Four means Five-TENS and Four ONES. This ties nicely into columnar adding without carrying. Count the TENS, count the ONES, relate how many of each you counted to the final sum and the structure of that number’s name and numerals.
Now we look at the teens. There are several issues with the teens. One issue is that they use a different suffix to imply a group of ten.The language of the teens has very little in the way of a pattern to latch on to. You might have noticed children who can count by ones in the 20s, 30s, and higher, but still struggle to say what comes after 11. So, it is important to make TEEN explicitly understood as One TEN, and when we count by tens we are really counting One TEN, Two TENs, Three TENs, and so on.
What’s worse, ELEVEN gives no clue to how many it is. Neither does TWELVE. So we have to look at the numerals 11 and 12, and question why it is that we don’t say TEEN for these numbers, even though they have the same numerical structure. The numbers really should be said as ONEteen and TWOteen.
Notice for 20 we say the TENS first, then we say the ONES. However, when we use the TEENS, we say the ONES first, then the TEN. Many children reverse their numbers because of this. If the language of our number system was a little more logical, we might say Teen-eight, Teen-nine, Twenty. Or better yet, we could say Onety-Four, Twenty-Four, Thirty-Four. So, in my class, I actually do use this language. Not always, and not exclusively, but I do use it.
What’s Ten plus Nine? It’s Ten and Nine more. It’s Teen-Nine. But because we have crazy English, it’s Nine-Teen.
This discussion of the language makes students meta-aware of the structure of our numbers and how they express those numbers.
I use conventional language and the invented naming interchangeably. You might be worried that this would cause students problems in the future, with accountants who can’t be understood because they learned how to count from crazy Mister Reed. But this isn’t the case. The predominant convention will dominate. Making the exceptions of our naming system explicit, we create a stronger understanding of the rules, and create connections between the names, numerals, and quantities which creates deeper understanding of number.