Tens and ones
By the end of this lesson a child reads a two-digit number by place. The left digit says how many tens there are. The right digit says how many ones there are.
What the child can do at the end
- For 34, say: 3 tens and 4 ones.
- Build 34 from three bundles of 10 and four loose sticks.
- Does not add the digits into 3 + 4 = 7, and does not write 304.
What the digits mean
In 34, the digit 3 does not mean three sticks. It means three groups of ten, which is 30. The digit 4 means four single sticks. Together: 30 + 4 = 34.
One problem, step by step
Build the number 34 with sticks.
- Look at the left digit: 3. Make three bundles, with exactly 10 sticks in each.
- Three bundles are 30. That is not 34 yet.
- Look at the right digit: 4. Add four sticks that are not in a bundle.
- 30 + 4 = 34. Check: count the bundles (3), then the loose sticks (4).
A common mistake
The child sees the digits 3 and 4 and says 34 means seven sticks, because 3 + 4 = 7. The digits are not added. Each digit has its own place. Three tens are 30, not 3.
The other mistake is writing 304 for “3 tens and 4 ones”. A zero would be its own digit in the tens place. 3 tens and 4 ones are written as 34.
Practice
- How many tens and how many ones are in 27?
- Which number is 5 tens and 0 ones?
- Which number is 1 ten and 9 ones?
- Which is worth more in 41: the tens digit or the ones digit?
Answers
- 2 tens and 7 ones
- 50
- 19
- The tens digit is 4 and is worth 40. The ones digit is 1 and is worth 1. The ten is worth more.
In 41 the digit 4 looks “like only four”, but it stands in the tens place, so it is worth forty.
After the lesson
When the child can build 34 without adding the digits, open addition with carrying. Carrying is the moment when ones become a new ten.
For a parent
Let every bundle of ten be the same color, and the loose sticks another color. Ask “how many bundles” first, and only then “how many loose ones”.