MathIsimple
Lesson 1-1: Three-Digit Addition

Three-Digit Addition

Master three-digit addition using place value alignment and regrouping strategies through interactive library book purchase scenarios.

45 minutesRegrouping StrategiesLibrary ScenariosPlace Value
Learning Scenario: School Library Book Purchase

The Problem:

Our school library wants to buy 246 storybooks and 138 science books. How many books will they have in total?

Library Book Addition Challenge

Step-by-Step Method:

Step 1: Align numbers by place value
Step 2: Add ones: 6 + 8 = 14
Step 3: Add tens: 4 + 3 + 1 = 8
Step 4: Add hundreds: 2 + 1 = 3

Learning Activities

Master three-digit addition through interactive activities and real-world scenarios

Knowledge Points Display
Activity 1
Learn three-digit addition with our friendly math teacher. Master place value alignment and regrouping strategies through interactive demonstrations.

Key Features:

  • Interactive place value demonstration
  • Step-by-step regrouping process
  • Visual addition strategies
  • Progress tracking with milestones

Skills You'll Learn:

  • Place value alignment: Hundreds, Tens, Ones
  • Regrouping: 10 ones = 1 ten, 10 tens = 1 hundred
  • Vertical addition: Line up digits correctly
  • Problem solving: Apply to real scenarios
Interactive Practice
Activity 2
Practice three-digit addition through library book purchase scenarios. Help calculate total books and manage inventory.

Key Features:

  • Library book purchase simulation
  • Interactive addition practice
  • Regrouping strategy application
  • Real-world problem solving

Skills You'll Learn:

  • 246 + 138 = 384 books (no regrouping needed)
  • 357 + 245 = 602 books (regrouping required)
  • Step 1: 7 + 5 = 12, write 2, carry 1
  • Step 2: 5 + 4 + 1 = 10, write 0, carry 1
Examples Library
Activity 3
Explore various three-digit addition problems and practice different regrouping scenarios.

Key Features:

  • Multiple problem types
  • Different regrouping scenarios
  • Step-by-step solutions
  • Interactive practice problems

Examples:

  • No regrouping: 234 + 152 = 386
  • Tens regrouping: 267 + 185 = 452
  • Hundreds regrouping: 456 + 378 = 834
  • Both regrouping: 789 + 456 = 1245
Regrouping Guide: Step-by-Step

Regrouping Rules:

Rule 1: 10 ones = 1 ten

When ones column adds to 10 or more

Rule 2: 10 tens = 1 hundred

When tens column adds to 10 or more

Rule 3: Always carry to the left

Write the carried digit above the next column

Example: 357 + 245

Step 1: Add ones

7 + 5 = 12, write 2, carry 1

Step 2: Add tens

5 + 4 + 1 = 10, write 0, carry 1

Step 3: Add hundreds

3 + 2 + 1 = 6, write 6

Answer: 602

357 + 245 = 602

Practice Examples

Library Book Problems:

Storybooks + Science Books: 246 + 138 = 384 books

Reference + Fiction: 189 + 267 = 456 books

Biography + History: 324 + 178 = 502 books

Art + Music: 156 + 234 = 390 books

Regrouping Scenarios:

No Regrouping: 234 + 152 = 386

Tens Regrouping: 267 + 185 = 452

Hundreds Regrouping: 456 + 378 = 834

Both Regrouping: 789 + 456 = 1245

Ready for the next lesson?

Next LessonUnit Overview