Grade 1 · Place Value · MAT-01-PV-001
Count to 120
Count forward to 120 starting at 1 or any given number less than 120.
Learning objectives
What you should be able to do
- Count forward to 120 starting at 1 or any given number less than 120.
- Identify missing numbers in sequences through 120.
- Explain how the counting sequence changes at decade boundaries such as 39 to 40 and 99 to 100.
Prerequisite check
Make sure the foundation is ready.
Checks Kindergarten counting-on fluency.
Checks transition into larger place-value patterns.
Learn
Build the idea from meaning, not memorization.
The counting sequence continues by one
Every next whole number is exactly one more than the number before it. This rule does not stop at 20; it continues through 120 and beyond.
Decade boundaries change the tens digit
After 29 comes 30, after 39 comes 40, and so on. When the ones reach 9 and one more is added, a new group of ten is formed.
Counting can start anywhere
If the task begins at 47, there is no need to restart at 1. Continue 48, 49, 50, 51. Starting in the middle strengthens understanding of sequence structure.
A hundred creates a new place-value pattern
After 99 comes 100. One hundred is ten groups of ten. The sequence then continues 101, 102, and so forth to 120.
Interactive math lab
Change it. See what stays true.
Number Line Explorer
Move along the number line.
4 is one less. 5 and 6 is one more.
- start anywhere
- cross decade
- cross hundred
- fill missing
Worked examples
Twenty different ways to see the concept work.
Count 21 to 25.
21,22,23,24,25Each number is one more.
Count 28 to 32.
28,29,30,31,32The sequence crosses a decade.
What comes after 39?
40One more completes another ten.
What comes after 49?
50The tens digit increases.
What comes after 59?
60Another group of ten is completed.
What comes after 69?
70One more than 69 is 70.
What comes after 79?
80The ones reset to zero.
What comes after 89?
90The next decade begins.
What comes after 99?
100Ten tens make one hundred.
Count 98 to 102.
98,99,100,101,102The rule stays one-more across 100.
Start at 43 and count five numbers including 43.
43,44,45,46,47Continue from the given start.
Fill 56,57,__,59.
58One number is missing.
Fill 68,69,__,71.
70The missing number crosses a decade.
Fill 98,99,__,101.
100One hundred follows ninety-nine.
Count 107 to 111.
107,108,109,110,111Counting continues past 100.
What is one more than 114?
115Increase by exactly one.
What is one less than 120?
119Move one step backward.
How many forward steps from 116 to 120?
4117,118,119,120.
Why does 29 become 30 after one more?
The 9 ones plus one form a new tenPlace value explains the digit change.
Why does counting past 100 still work the same way?
Whole numbers still increase by oneThe symbols change, but the sequence rule does not.
Practice
Guided practice with hints
01Count 37 to 42.
Hint: Watch the change after 39.
Answer: 37,38,39,40,41,42
02What comes after 99?
Hint: Think ten groups of ten.
Answer: 100
03Fill 108,109,__,111.
Hint: Continue by one.
Answer: 110
04Start at 73 and say next four numbers.
Hint: Do not restart at 1.
Answer: 74,75,76,77
05What is one less than 100?
Hint: Move backward once.
Answer: 99
06Explain 49→50.
Hint: Nine ones plus one forms another ten.
Answer: 50 begins the next decade.
Practice
Independent practice
01After 29
Answer: 30
02After 79
Answer: 80
03After 99
Answer: 100
04Fill 84,85,__,87
Answer: 86
05Fill 118,119,__
Answer: 120
06Count 96 to 101
Answer: 96,97,98,99,100,101
07One more than 109
Answer: 110
08One less than 120
Answer: 119
Common mistakes
Learn to catch the error, not just the answer.
Use place-value groups to show that ten ones regroup into one ten.
Begin directly with the stated number and continue.
Practice 98,99,100,101,102 as one continuous chain.
Applications & challenge
Use the idea beyond a single exercise.
Applications
- Use a 120 chart to track classroom counts and locate missing numbers.
- Count collections in organized groups while continuing beyond 100.
Challenge problems
Count from 87 through 103.
87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103
What number is 7 steps after 113?
120
Explain why decade changes happen after numbers ending in 9.
Adding one creates ten ones, which regroup as one additional ten.
What pattern do the ones digits follow as you count?
0 through 9 repeat while higher place values change as groups are completed.
Flashcards
Retrieve it from memory.
Flashcards
Card 1 of 6
Game mode
Road to 120
Repair missing sections of a 1–120 number path and cross decade/hundred boundaries correctly.
Practice
Mastery check
01Count 28 to 32.
Answer: 28,29,30,31,32
02After 59
Answer: 60
03After 99
Answer: 100
04Fill 107,108,__,110
Answer: 109
05Count 117 to 120
Answer: 117,118,119,120
06One less than 100
Answer: 99
07Why does 89→90?
Answer: Adding one to nine ones creates the next ten.
08Why can you start counting at 74?
Answer: The sequence is fixed, so you can continue from any known position.
Terminology
Words to know
- decade
- A group or interval organized by tens, such as the 30s.
- hundred
- A quantity equal to ten tens or one hundred ones.
- sequence
- An ordered list following a rule.
- place value
- The value a digit has because of its position.
Continue learning
Connected concepts
Curriculum references
Standards and instructional references
California Common Core State Standards for Mathematics — Grade 1 Number & Operations in Base Ten
Grade 1 counting, place value, numeral representation, and comparison progression.