Week 13 Teacher Guide: 3-Digit Addition & Subtraction

Phase 2: Addition & Subtraction to 100

Week 13: 3-Digit Addition & Subtraction

Key Skills: Hundreds place; regrouping across zeros

Learning Objectives

• Add and subtract 3-digit numbers without regrouping
• Add and subtract 3-digit numbers with regrouping
• Understand place value in the hundreds
• Solve word problems with 3-digit numbers
• Check work using inverse operations

Daily Breakdown

Monday: 3-Digit Addition (No Regrouping)

Focus: Introduce the hundreds place. Students add 3-digit numbers without regrouping.

Key Concept: Add ones, then tens, then hundreds — same as 2-digit, just one more column.

Hands-on: Use base-ten blocks to show hundreds flats, tens rods, and ones cubes.

Tuesday: 3-Digit Addition with Regrouping

Focus: Regrouping from ones to tens, and tens to hundreds.

Key Concept: When a column adds to more than 9, carry to the next column.

Common Error: Forgetting to add the carried number. Have students circle carries.

Wednesday: 3-Digit Subtraction

Focus: Subtraction without regrouping, then with regrouping.

Key Concept: Borrow from the next column when you can't subtract.

Hands-on: Use base-ten blocks to physically trade a hundred for ten tens, or a ten for ten ones.

Thursday: Word Problems

Focus: Apply 3-digit addition and subtraction to real-world problems.

Key Concept: Identify whether to add or subtract based on keywords (left, remaining = subtract; total, altogether = add).

Challenge: Two-step problems requiring both operations.

Friday: Review & Assessment

Focus: Mixed practice and self-assessment.

Key Concept: Check work using inverse operations (addition checks subtraction, subtraction checks addition).

Assessment: Self-check emojis help students reflect on their confidence.

Answer Key

Monday

Section 2: 377, 567, 359, 737, 377, 477

Section 5: 477, 486, 387, 587, 558, 484

Tuesday

Section 2: 412, 604, 563, 701

Section 3: 415, 605, 503, 623, 623, 464

Section 4: Mistake 1: forgot to carry; Answer: 412. Mistake 2: forgot to carry; Answer: 604

Section 5: 435, 631, 543, 616, 624, 463

Wednesday

Section 2: 222, 211, 222, 222, 222, 202

Section 5: 258, 254, 255, 258

Section 6: 256, 256, 256, 259, 256, 278

Thursday

Section 1: 222 books, $158

Section 2: 256 apples, 159 toys

Section 3: 633 feet, 387 toys, 157 students, 172 pages

Section 4: 315, 209, 209 cookies left

Friday

Section 1: 412, 604, 563, 701, 623, 464

Section 2: 256, 256, 256, 259, 256, 278

Section 3: 612, 345, 645, 278, 635, 252

Section 4: 167, 333, 278, 334

Section 5: 345, 734

Teaching Tips

• Use manipulatives: Base-ten blocks are essential for understanding regrouping in 3-digit numbers.
• Emphasize place value: Remind students that the hundreds column works the same as tens and ones.
• Circle carries and borrows: Have students circle numbers they carry or borrow to avoid forgetting.
• Check work: Teach students to check addition with subtraction and vice versa.
• Borrowing across zero: This is tricky — use visual aids showing 100 becoming 9 tens and 10 ones.

Differentiation

Support: Provide 2-digit review problems first. Use color-coded place value charts.

Extension: Challenge students with 4-digit numbers or problems borrowing across zeros (e.g., 502 - 167).