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Counting by tens to thirty
Discover Mathematics: Chapter 5
GoalCount by tens to 30, see 30 as three tens, and write 30.
New words
ten · a full group of 10twenty · two tensthirty · three tenscount by tens · say 10, 20, 30 as you go
Explanation
Counting one by one takes a long time. When things are in full groups of ten, we can count by tens. One full group is ten. Two full groups are twenty. Three full groups are thirty. We say: ten, twenty, thirty. The number 30 is written with a 3 and a 0, because there are 3 tens and no ones left over.
Worked examples
One full ten-frame holds 10 dots. That is one ten.
Two full ten-frames hold 20 dots. We count by tens: ten, twenty.
Mayar packs 30 oranges in rows of ten. Count the rows by tens: 10, 20, 30.
Class activity
Tens with beans. Give the child 30 dry beans or small stones. Make piles of ten, counting each pile aloud. Then count the piles by tens: ten, twenty, thirty. Mix them up and try again with the child doing all of it.
Practice
1
Count by tens: 10, 20, … What number comes next?
30
2
How many stars are there? Count each row of ten.
30
3
How many flowers are there? Count by tens.
20
4
Say the tens in order, from ten up to thirty.
10, 20, 30
5
Write the number for 3 tens.
30