Learning to Read and Write Numbers to 120 in Grade 1

Master reading and writing numbers to 120: place value, number words, and expanded form through these 3 detailed exercises.

Solution: Exercises 1 to 3
1 Place Value
Exercise 1
What is the value of each digit in the number 87?
Write it in expanded form.
Definition:

Place value: In a 2-digit number, the left digit represents TENS and the right digit represents ONES.

Place value method:
  1. Identify the tens digit (leftmost)
  2. Identify the ones digit (rightmost)
  3. Write in expanded form: tens × 10 + ones
Number
87
Tens
8
Ones
7
Expanded
80 + 7
Step 1: Identify the digits

In 87, the tens digit is 8 and the ones digit is 7

Step 2: Calculate the value of each digit

Tens place: 8 × 10 = 80, Ones place: 7 × 1 = 7

Step 3: Write in expanded form

87 = 80 + 7

87 has 8 tens and 7 ones
Final answer:

87 = 80 + 7 (8 tens and 7 ones)

Applied rules:

• Place value: Each position has a specific value (tens, ones)

• Expanded form: Shows the value of each digit

• Addition: Combine the values to get the original number

TENS PLACE
8
= 80
ONES PLACE
7
= 7
2 Number Words
Exercise 2
Write the number word for 94.
Then write the number for "one hundred four".
Definition:

Number words: Writing numbers using letters (words) instead of digits.

Number
94
Word
ninety-four
Reverse
104
Step 1: Break down 94

94 has 9 tens (ninety) and 4 ones (four)

Step 2: Combine with hyphen

Ninety + four = ninety-four

Step 3: Convert "one hundred four"

One hundred = 100, four = 4, so 100 + 4 = 104

94 = ninety-four
one hundred four = 104
Final answer:

94 = ninety-four
one hundred four = 104

Applied rules:

• Hyphens: Use hyphens for compound numbers 21-99

• Hundreds: Say "hundred" after the hundreds digit

• Special cases: Eleven through nineteen are unique

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3 Expanded Form
Exercise 3
Write 107 in expanded form.
Then write the standard form for 100 + 0 + 5.
Definition:

Expanded form: Writing a number to show the value of each digit (hundreds + tens + ones).

Number
107
Expanded
100 + 0 + 7
Reverse
105
Step 1: Identify each digit's place

In 107: 1 is in hundreds place, 0 in tens place, 7 in ones place

Step 2: Write expanded form

107 = 100 + 0 + 7 (1 hundred + 0 tens + 7 ones)

Step 3: Convert expanded to standard

100 + 0 + 5 = 105

Step 4: Verify the result

105 has 1 hundred, 0 tens, 5 ones: 100 + 0 + 5 ✓

107 = 100 + 0 + 7
100 + 0 + 5 = 105
Final answer:

107 = 100 + 0 + 7
100 + 0 + 5 = 105

Applied rules:

• Place value: Each position has a specific value (hundreds, tens, ones)

• Zero placeholder: Even zeros have a place value

• Standard form: Regular numeric representation

HUNDREDS
1
= 100
TENS
0
= 0
ONES
7
= 7
Rules and methods, laws,...
87 = 80 + 7
Place Value
Ones
0-9
Rightmost digit
Tens
10-90
Second from right
Hundreds
100-120
Third from right
Key definitions:

Place value: The value of a digit based on its position in a number

Expanded form: Writing a number showing the value of each digit

Standard form: Regular numeric representation (123)

Complete methodology:
  1. Identify positions: Recognize hundreds, tens, and ones places
  2. Find digit values: Multiply each digit by its place value
  3. Combine values: Add the place values together
  4. Verify: Check that the expanded form equals the original number
Tip 1: Count by tens to reach numbers: 10, 20, 30... up to 120.
Tip 2: Use base-10 blocks to visualize tens and ones.
Tip 3: Remember that numbers 11-19 have special names.
Tip 4: When writing number words, use hyphens for compound numbers like twenty-one.
Common errors: Forgetting zero placeholders, misreading teen numbers, confusing tens and ones.
Practice strategies: Count objects in groups of ten, write numbers daily, use number lines.
Rules to know:

• Place value order: Hundreds, Tens, Ones (from left to right)

• Number words: Hyphens connect tens and ones (thirty-two)

• Expanded form: Shows each digit's value separately

• Zero placeholder: Even if a place has 0, include it in expanded form

Key Concepts and Practice Patterns
120 = 100 + 20 + 0
Expanded Form
Understanding Number Patterns:

Counting sequence: Numbers increase by one from 1 to 120

Tens pattern: Every ten numbers, the tens digit increases by one

Number families: Similar patterns in numbers (20s, 30s, etc.)

Reading Strategies:
  1. Look at the number of digits: 1-digit, 2-digit, or 3-digit
  2. Identify place values: Hundreds, tens, ones
  3. Read from left to right: Start with the highest place value
  4. Combine parts: Read each group correctly
Pattern Recognition: Notice that numbers ending in the same digit form vertical columns on a 100 chart.
Memory Aid: Think of "teen" numbers as "ten" plus another number (thirteen = ten + three).
Visual Help: Draw groups of ten objects to represent tens.
Number Relationships: Each number is one more than the previous number.
Base-10 System: Our number system is based on groups of ten.
Important Patterns:

• Teen numbers: 11-19 (eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen)

• Ty numbers: 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120

• Compound numbers: Use hyphens (twenty-one, thirty-five, etc.)

• Hundreds: One hundred, one hundred one, one hundred two, ..., one hundred twenty

Additional Practice Problems
113 = 100 + 10 + 3
Example Problem
Practice Problems:

Problem 1: Write 115 in expanded form.

Problem 2: Write the number word for 108.

Problem 3: What number is represented by 90 + 6?

Solution Approach:
  1. For expanded form: Identify each digit's place value
  2. For number words: Break into hundreds, tens, and ones
  3. For standard form: Add the expanded parts together
Tip 1: Practice counting forward and backward from any number to 120.
Tip 2: Use a number line to visualize the relationship between numbers.
Tip 3: Group objects in tens to understand place value better.
Tip 4: Read number words aloud to reinforce the connection between digits and words.
Assessment Focus: Teachers often test understanding of place value and number words.
Real-world Application: These skills help with money counting and measurement.
Practice Solutions:

• 115 in expanded form: 100 + 10 + 5

• Number word for 108: one hundred eight

• 90 + 6: 96

Questions & Answers

Question: I don't understand why 100 is called "one hundred" but then 101 is "one hundred one" instead of "one hundred and one". Can you explain the difference?

Answer: Great observation! The way we say numbers follows specific patterns:

  • For exact hundreds like 100, 200, 300, we just say "one hundred", "two hundred", "three hundred"
  • For numbers with extra ones, like 101, 102, 103, we add the ones part: "one hundred one", "one hundred two", "one hundred three"
  • We don't typically use "and" when reading whole numbers unless we're talking about decimals

So the pattern is: [hundreds] + [tens and ones]. For 100, there are no tens or ones beyond the hundred, so we just say "one hundred". For 101, we have one hundred plus one more, so we say "one hundred one".

Examples: 100 = one hundred, 101 = one hundred one, 105 = one hundred five, 110 = one hundred ten

Question: My child gets confused between numbers like 40 and 14. They look similar. How can I help them understand the difference?

Answer: This is very common! The similarity in digits can be confusing. Here's how to help:

  • Emphasize place value: 40 has 4 tens and 0 ones (forty), while 14 has 1 ten and 4 ones (fourteen)
  • Use manipulatives: Show 4 groups of ten blocks vs. 1 group of ten and 4 single blocks
  • Focus on the names: "Forty" sounds different from "fourteen" - emphasize the "-ty" vs "-teen" endings
  • Practice with number lines: Show the large gap between 14 and 40

Remember that "teen" numbers (11-19) are unique and don't follow the regular pattern. After 19, we go back to regular patterns: twenty, thirty, forty, etc.

Visual aids like base-10 blocks or drawings can make the difference clear: 40 is four rods of ten, while 14 is one rod of ten plus four individual units.

Question: Why do we need to learn numbers up to 120? Why not stop at 100?

Answer: Great question! Learning numbers up to 120 helps you in many ways:

  • Building confidence: It extends the pattern you learned up to 100, showing you can handle bigger numbers
  • Real-world applications: You might count more than 100 items (like books, toys, or students in school)
  • Preparation for addition: When adding larger numbers, you'll go past 100
  • Understanding patterns: It shows that the same place value system continues beyond 100

Think of it like learning to count higher on a ladder - once you know 1-100, going to 120 is just continuing the same pattern. It also prepares you for learning about hundreds later!

Plus, many classrooms have over 100 students when combining multiple grades, so being able to count higher is practical!