Activities on Composing and Decomposing Numbers in Grade 1

Master composing and decomposing numbers: place value, tens and ones, number bonds, base ten blocks through these 5 detailed activities designed for young learners.

Composing and Decomposing: Rules and Methods
🔢 Composing & Decomposing 🔢
10
Tens
1
Ones
15
1T + 5O
Key Definitions:

Composing: Putting numbers together to make a larger number

Decomposing: Breaking apart a number into smaller parts

Place Value: Where a digit sits tells its value (tens, ones)

Base Ten: Our number system uses groups of 10

Number = Tens + Ones
Place Value Formula
Step-by-Step Method:
  1. Identify the number: Look at the total number
  2. Find tens: Count how many groups of 10 fit
  3. Find ones: Count remaining units
  4. Write as equation: Number = Tens + Ones
Tip 1: Use your fingers to group into tens!
Tip 2: Draw circles in groups of 10.
Tip 3: Say "___ tens and ___ ones" aloud.
Important: Every number can be broken into tens and ones.
Remember: 10 ones = 1 ten, 10 tens = 1 hundred.
Activity: Numbers 1-3
1 Composing Numbers
Activity 1
Build the number 14 using tens and ones. How many tens and ones do you need?
Definition:

Composing: Building a number from its parts

Method:
  1. Look at the number (14)
  2. Count how many tens (10)
  3. Count how many ones (4)
  4. Put them together: 10 + 4 = 14
10
1
1
1
1
Number
14
Tens
1
Ones
4
Step 1: Identify the number

We want to build the number 14

Step 2: Find how many tens

How many groups of 10 are in 14? Only 1 group of 10

Step 3: Find how many ones

After taking away 10, we have 4 left over

Step 4: Write the equation

14 = 10 + 4 (1 ten and 4 ones)

14 = 1 ten + 4 ones
Final answer:

14 is made of 1 ten and 4 ones

Applied rules:

• Place value: Tens and ones positions

• Grouping: Count by tens first

• Composition: Parts make whole number

2 Decomposing Numbers
Activity 2
Break apart the number 17 into tens and ones. What parts do you get?
Definition:

Decomposing: Breaking a number into parts

10
1
1
1
1
1
1
1
Number
17
Tens
1
Ones
7
Step 1: Start with the number

We have the number 17

Step 2: Take out groups of 10

How many tens are in 17? Only 1 group of 10

Step 3: Count the leftover ones

After taking away 10, we have 7 ones left

Step 4: Write the decomposition

17 = 10 + 7 (1 ten and 7 ones)

17 = 1 ten + 7 ones
Final answer:

17 breaks apart into 1 ten and 7 ones

Applied rules:

• Decomposition: Breaking into place value parts

• Subtraction: 17 - 10 = 7

• Place value: Tens and ones positions

3 Number Bonds
Activity 3
Show different ways to make the number 12 using addition. Find at least 3 ways.
Definition:

Number bonds: Different ways to compose a number

Way 1
10+2
Way 2
9+3
Way 3
8+4
Step 1: Think about the target number

We want to make 12 in different ways

Step 2: Start with place value

12 = 10 + 2 (standard place value)

Step 3: Find other combinations

12 = 9 + 3, 8 + 4, 7 + 5, 6 + 6

Step 4: Check your work

Add each pair to make sure it equals 12

12 = 10+2, 9+3, 8+4, 7+5, 6+6
Final answer:

Multiple ways to make 12: 10+2, 9+3, 8+4, etc.

Applied rules:

• Flexibility: Numbers can be composed multiple ways

• Addition: Combine parts to make whole

• Verification: Check each combination

Activity: Numbers 4-5
4 Base Ten Blocks
Activity 4
Show the number 23 using base ten blocks. How many tens and ones do you need?
Definition:

Base ten blocks: Visual representation of place value

10
10
1
1
1
Number
23
Tens
2
Ones
3
Step 1: Look at the number

We need to represent 23

Step 2: Count the tens

How many tens are in 23? 2 tens (20)

Step 3: Count the ones

After 20, we need 3 more to make 23

Step 4: Represent with blocks

2 ten blocks + 3 one blocks = 23

23 = 2 tens + 3 ones
Final answer:

23 needs 2 ten blocks and 3 one blocks

Applied rules:

• Base ten: Each ten block = 10 ones

• Visualization: Physical representation

• Place value: Position determines value

5 Mixed Practice
Activity 5
Complete these number sentences: 19 = ___ tens + ___ ones, 35 = ___ tens + ___ ones
Definition:

Mixed practice: Applying concepts to various problems

Problem 1
19 = ?
Problem 2
35 = ?
Answers
1T+9O, 3T+5O
Step 1: Analyze first problem

19 = ? tens + ? ones

Step 2: Solve first problem

19 has 1 ten and 9 ones

Step 3: Analyze second problem

35 = ? tens + ? ones

Step 4: Solve second problem

35 has 3 tens and 5 ones

19 = 1 ten + 9 ones, 35 = 3 tens + 5 ones
Final answer:

19 = 1 ten + 9 ones, 35 = 3 tens + 5 ones

Applied rules:

• Place value: Determine tens and ones

• Systematic approach: Work left to right

• Verification: Check final answers

Composing and Decomposing Numbers: Complete Guide

What Are Composing and Decomposing?

Composing means putting numbers together to make a bigger number. Example: 10 + 4 = 14

Decomposing means breaking apart a number into smaller pieces. Example: 14 = 10 + 4

Why Learn This?

Understanding how numbers are made helps with addition, subtraction, and understanding larger numbers. It builds strong number sense!

Place Value System

  • Ones place: Single digits (0-9)
  • Tens place: Groups of 10 (10, 20, 30...)
  • Each place is 10 times bigger than the one before

Tools We Use

Base Ten Blocks: Long rods = 10, small cubes = 1
Number Bonds: Circles showing parts that make a whole
Tens and Ones: Breaking numbers into place value parts

How to Compose Numbers

Start with parts and put them together:

  1. Have 1 ten and 3 ones → 10 + 3 = 13
  2. Have 2 tens and 7 ones → 20 + 7 = 27
  3. Have 4 tens and 0 ones → 40 + 0 = 40

How to Decompose Numbers

Start with a number and break it apart:

  1. 16 = 10 + 6 (1 ten and 6 ones)
  2. 28 = 20 + 8 (2 tens and 8 ones)
  3. 45 = 40 + 5 (4 tens and 5 ones)

Real World Examples

  • 12 pencils = 1 group of 10 + 2 extra = 1 ten + 2 ones
  • 24 students = 2 groups of 10 + 4 extra = 2 tens + 4 ones
  • 37 toys = 3 groups of 10 + 7 extra = 3 tens + 7 ones

Key Strategies for Success

  • Count by tens first: 10, 20, 30, 40...
  • Then count ones: 31, 32, 33, 34...
  • Use visual aids: Draw dots in groups of 10
  • Practice with objects: Count actual items

Common Mistakes to Avoid

  • Mixing up tens and ones positions
  • Not counting all the tens
  • Forgetting to include the zeros
  • Adding instead of subtracting when decomposing

Questions & Answers

Question: I don't understand why we need to break numbers apart. Why can't we just count normally?

Answer: Great question! Breaking numbers apart helps us understand how numbers work, just like taking apart a toy to see how it works!

  • When you know that 15 is "1 ten and 5 ones," adding becomes easier: 15 + 3 = 1 ten + 5 ones + 3 ones = 1 ten + 8 ones = 18
  • It helps with big numbers later: knowing that 123 is 1 hundred, 2 tens, and 3 ones
  • It makes mental math faster and easier

Think of it like organizing your toys: it's easier to find what you need when things are grouped together!

Question: My child is struggling with the concept of tens and ones. How can I help them visualize this?

Answer: Use hands-on materials to make it concrete!

  • Use straws or craft sticks: bundle 10 together with a rubber band to make "1 ten"
  • Use coins: dimes are tens, pennies are ones
  • Draw circles in groups of 10, then count extras
  • Use fingers: 1 hand = 5, 2 hands = 10

Start with small numbers (11-19) since these are the "teen" numbers that clearly show the tens + ones pattern. Practice daily with real objects!

Question: What are some fun activities to reinforce composing and decomposing skills?

Answer: Make it playful and engaging!

  • Number Bond Flowers: Draw flowers where petals add up to center number
  • Base Ten Block Buildings: Build structures with tens and ones
  • Shopping Game: Use play money to "buy" items of different values
  • Dot Patterns: Arrange dots in groups of 10 and count extras
  • Number Puzzles: Match numbers to their tens + ones representations

The key is repetition through fun activities rather than drill-and-practice worksheets!