3
Eighty-one to one hundred
Joyful Mathematics: Chapter 8
GoalRead and write the numbers from 81 to 99, and know 100.
New words
ninety · the name for 9 tens, written 90one hundred · 10 tens, written 100ninety-nine · the biggest number before 100
Explanation
Nine tens make 90, ninety. 9 tens and 9 ones make 99, ninety-nine. Add one more one and the ones make a new ten. Now there are 10 tens. 10 tens make one hundred, written 100.
Worked examples
8 tens and 6 ones make eighty-six.
9 tens and 9 ones make ninety-nine.
Ninety-nine and one more makes one hundred.
Class activity
Count to a hundred. Clap and count in tens: 10, 20, 30 up to 100. How many claps did you make? Then count slowly from 91 to 100, one number for each step you take.
Practice
1
Which number is this?
93
2
Write 9 tens and 4 ones as a number.
94
3
Write eighty-eight as a number.
88
4
What comes after 99?
100, one hundred.
5
How many tens make 100?
10