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From sixty to a hundred
Discover Mathematics: Chapter 7
GoalRead and write the numbers 60 to 99, and know that 100 comes next.
New words
sixty · six tensseventy · seven tenseighty · eight tensninety · nine tenshundred · ten tens
Explanation
Sixty is six tens, seventy is seven tens, eighty is eight tens and ninety is nine tens. A number between them has some ones as well. 68 is six tens and eight ones. The last number with nine tens is 99, which is nine tens and nine ones. One more than 99 makes a new ten, and we have ten tens. That is one hundred, written 100.
Worked examples
Adam shows 75 with sticks and cubes: 7 sticks and 5 cubes.
Yara counts 62 oranges at the market: 6 tens and 2 ones.
99 is 9 sticks and 9 cubes. One more cube makes a tenth stick, and that is 100.
Class activity
Hundred hop. Draw a line of 10 big steps on paper or with chalk, and write 10, 20, 30 up to 100 on them. The child hops along and says each number. Then hop from 60 to 70, one number at a time, saying each one.
Practice
1
How many balloons are there? Count the rows of ten and the ones.
61
2
What number comes after 79?
80
3
Look at the sticks and cubes. Write the number.
94
4
What number comes after 99?
100
5
Count by tens: 60, 70, __, 90. What is missing?
80