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Counting up to forty
Discover Mathematics: Chapter 6
GoalCount by ones and by tens to 40, and see 40 as four tens.
New words
forty · four tenscount on · start from a number and say the next onesby tens · jumping 10, 20, 30, 40
Explanation
Now we can count all the way to forty. We can count by ones: 1, 2, 3 and so on up to 40. We can also count by tens: ten, twenty, thirty, forty. Look at the kites in four rows of ten. Four full tens make forty. We write 40 with a 4 for the tens and a 0 for the ones, because no ones are left over.
Worked examples
Rahma hangs 40 lanterns along the street for Ramadan. Four rows of ten: 10, 20, 30, 40.
Four sticks, each a ten, show 40. There are no cubes, so the ones digit is 0.
Adam counts his footprints from the door to the bus stop, by tens: 10, 20, 30, 40.
Class activity
Count and jump. Count aloud from 1 to 40, and jump once on every tenth number. Then count by tens only, with a big step on each number. Let the child lead and the grown-up clap.
Practice
1
How many pears are there? Count by tens.
40
2
Count by tens: 10, 20, 30, … What comes next?
40
3
What number comes after 39?
40
4
How many tens are in 40?
4 tens
5
Count on from 36: 36, 37, __, __, 40. Which numbers are missing?
38 and 39