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Mastering Three-Digit Addition: Strategies for Success

Lesson Plan
Grade 3
English

Mastering Three-Digit Addition: Strategies for Success

Lesson Plan: Three-Digit Addition Within 1,000

Duration: 45 Minutes Grade Level: Grade 3 Subject: Mathematics Standard: CCSS 3.NBT.A.2: Fluently add and subtract within 1,000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.


I. Lesson Objective

Students will be able to add two three-digit numbers within 1,000 by applying three distinct strategies: base-ten drawings, open number lines, and the standard algorithm.

II. Materials

  • Base-ten blocks (hundreds flats, tens rods, ones units)
  • Individual whiteboards and markers
  • Strategy Reference Sheet (Worksheet)
  • Exit Ticket slips
fig 1: Physical base-ten blocks used for concrete modeling
fig 1: Physical base-ten blocks used for concrete modeling



III. The Hook: Strategy Showdown (5 mins)

Present the problem: 345 + 127.
Show two different ways to solve it side-by-side (using the visuals below). Ask students: "Which one looks easier to you? Why?" Discuss how the base-ten drawing helps us 'see' the numbers, while the number line helps us 'jump' through the numbers.
Strategy A: Base-Ten Drawing
fig 2: 345 + 127 shown with base-ten sketches
fig 2: 345 + 127 shown with base-ten sketches

Strategy B: Open Number Line
fig 3: 345 + 127 solved by jumping on a number line
fig 3: 345 + 127 solved by jumping on a number line



IV. Gradual Release Instruction (30 mins)

1. Direct Instruction (I Do): Base-Ten Drawings (10 mins)

  • Goal: Connect concrete blocks to representational drawings.
  • Modeling: Solve
    
    .
  • Draw 2 squares (hundreds), 5 lines (tens), and 8 dots (ones).
  • Draw 1 square, 3 lines, and 4 dots.
  • Key Concept: Regrouping. Circle 10 dots to make a new line. Count the total: 3 hundreds, 9 tens, 2 ones = 392.

2. Guided Practice (We Do): Open Number Line (10 mins)

  • Goal: Efficiently skip-count by place value.
  • Practice:
    
    .
  • Start at 456. Jump +200 (to 656), then +30 (to 686), then +5 (to 691).
  • Check for Understanding: Have students show their "jumps" on whiteboards.

3. Independent Practice (You Do): Standard Algorithm (10 mins)

  • Goal: Fluency and precision.
  • Introduce lining up place values. Solve
    
    .
  • Students complete the Addition Strategy Worksheet provided below.


V. Differentiation & EL Scaffolds

Tier
Strategy/Scaffold
Tier 1 (Support)
Provide pre-drawn base-ten grids; use 2-digit addition first to build confidence.
Tier 2 (Targeted)
Focus on regrouping transitions; use color-coded columns for hundreds, tens, and ones.
Tier 3 (Extension)
Solve 3-digit addition word problems with missing addends (e.g.,

).
EL Scaffold
Sentence Frames: "First, I added the ______. I had to regroup because ______." Use visual vocabulary cards for Sum, Regroup, Addend.


VI. Exit Ticket (5 mins)

  1. Which is the correct sum for 482 + 219 using the standard algorithm? A. 701 B. 711 C. 601 D. 691
  1. When using a number line to solve 350 + 120, what is the most efficient first jump? A. Jump +20 B. Jump +100 C. Jump +1 D. Jump +10


VII. Embedded Worksheet

Name:
Date:

Sequence Chain: Addition Strategy Practice

Solve the problem 456 + 287 using the sequence of strategies we learned today.

1. Base-Ten Drawing
2. __________
3. Standard Algorithm
Stage 1: Sketch your base-ten blocks (remember to regroup!):
Stage 2: Draw your number line and show your jumps:
Stage 3: Solve using vertical alignment: