Extending the Sequence: 101 to 120 - First Grade Mathematics
Many people think that counting stops when you reach 100, but in first grade, you have the special power to journey beyond 100 all the way to 120! Once you cross the magical border of 100, the exact same counting rules and patterns you already know start over again, with one hundred leading the way. Understanding numbers from 101 to 120 helps you see that numbers go on and on, building a sturdy bridge into second grade math. In this chapter, you will master reading, writing, and reciting the numbers from 101 to 120.
Crossing the 100 Threshold: 101 to 110
Crossing past 100 is just like beginning at 1 again, but with "one hundred" in front of every number word.
Numbers from 100 to 110:
100 -> One Hundred
101 -> One Hundred One
102 -> One Hundred Two
103 -> One Hundred Three
104 -> One Hundred Four
105 -> One Hundred Five
106 -> One Hundred Six
107 -> One Hundred Seven
108 -> One Hundred Eight
109 -> One Hundred Nine
110 -> One Hundred Ten
The Role of the Zero in the Middle
Look closely at the numeral 105. It has three digits: a 1 in the hundreds place, a 0 in the tens place, and a 5 in the ones place. The zero in the middle is an essential placeholder. It tells us: "There is one hundred, NO extra full tens, and five single ones." If you forgot the zero, you would accidentally write 15 instead of 105!
Reading Without Saying "And"
When reading numbers like 104, say "one hundred four." In mathematics, we do not say "one hundred and four," because the word "and" is saved for decimal points when you are older. Keep it clean: "one hundred one, one hundred two, one hundred three!"
The Extended Teens: 111 to 120
Once you reach 110, the teen patterns you learned in Unit 1 return, paired with one hundred.
Numbers from 111 to 120:
111 -> One Hundred Eleven (1 Hundred, 1 Ten, 1 One)
112 -> One Hundred Twelve (1 Hundred, 1 Ten, 2 Ones)
113 -> One Hundred Thirteen (1 Hundred, 1 Ten, 3 Ones)
114 -> One Hundred Fourteen (1 Hundred, 1 Ten, 4 Ones)
115 -> One Hundred Fifteen (1 Hundred, 1 Ten, 5 Ones)
116 -> One Hundred Sixteen (1 Hundred, 1 Ten, 6 Ones)
117 -> One Hundred Seventeen (1 Hundred, 1 Ten, 7 Ones)
118 -> One Hundred Eighteen (1 Hundred, 1 Ten, 8 Ones)
119 -> One Hundred Nineteen (1 Hundred, 1 Ten, 9 Ones)
120 -> One Hundred Twenty (1 Hundred, 2 Tens, 0 Ones)
Writing the Three Digits Accurately
Look at the numeral 116. The first 1 stands for 100. The second 1 stands for 10. The 6 stands for 6 ones. Together, they make one hundred sixteen. Look at 120. The 1 stands for 100, the 2 stands for 20 (2 tens), and the 0 stands for 0 ones.
The Bottom Rows of a 120 Chart
A 120 chart extends the standard 100 chart by adding two extra rows at the bottom.
The Extended Rows on a 120 Chart:
Row 10: 91 92 93 94 95 96 97 98 99 100
Row 11: 101 102 103 104 105 106 107 108 109 110
Row 12: 111 112 113 114 115 116 117 118 119 120
Vertical Column Alignment
Notice how 101 sits directly below 91, and 111 sits directly below 101. Every column continues its downward pattern of adding ten (+10)!
Practice Exercises
Exercise 1: Write the numeral for each of these number words: one hundred three, one hundred eight, one hundred fourteen, one hundred twenty.
Exercise 2: What number comes immediately after 109? What number comes immediately after 119?
Exercise 3: A student wrote "one hundred seven" as 17. What mistake did the student make, and what is the correct way to write the numeral?
Exercise 4: Count forward from 112 to 118. Write out all the numbers in the sequence.
Solutions and Explanations
Solution to Exercise 1: One hundred three is written as 103. One hundred eight is written as 108. One hundred fourteen is written as 114. One hundred twenty is written as 120.
Solution to Exercise 2: The number immediately after 109 is 110. The number immediately after 119 is 120.
Solution to Exercise 3: The student forgot the placeholder zero in the tens place. The numeral 17 represents seventeen (1 ten and 7 ones). One hundred seven has 1 hundred, 0 tens, and 7 ones, so it must be written with three digits as 107.
Solution to Exercise 4: Counting forward from 112 to 118: 112, 113, 114, 115, 116, 117, 118.