Lesson Plan
Subtraction Sleuths Unite Lesson Plan
Students will master multi-digit subtraction with regrouping by solving themed detective case problems, accurately subtracting numbers up to four digits in real-world contexts.
This lesson builds foundational computational skills and confidence by framing subtraction as detective work, making practice engaging and relevant to everyday tasks like shopping and budgeting.
Audience
5th Grade
Time
30 minutes
Approach
Hands-on detective-themed subtraction scenarios
Materials
- Detective Case Worksheets, - Answer Key for Detective Cases, - Individual Student Dry-Erase Boards, - Whiteboard and Markers, - Scratch Paper, and - Timer or Stopwatch
Prep
Prepare Materials
10 minutes
- Print enough copies of Detective Case Worksheets for each student and one master set of Answer Key for Detective Cases
- Gather individual dry-erase boards, markers, and erasers for all students
- Set up the classroom timer or stopwatch within easy view
- Review the subtraction problems and answers to anticipate common student questions
Step 1
Introduction
5 minutes
- Pose a mystery scenario: a shopper budgeted $1,234 but spent $789. What’s left?
- Explain that students are "subtraction sleuths" solving real-world puzzles
- Review key regrouping steps on the whiteboard with a simple example (e.g., 4,302 – 1,789)
- Reinforce vocabulary: minuend, subtrahend, difference
Step 2
Guided Practice
10 minutes
- Distribute Detective Case Worksheets
- Work through the first two problems together, projecting them on the whiteboard
- Call on volunteers to explain each regrouping step as they solve on individual dry-erase boards
- Check answers against the Answer Key for Detective Cases and address misconceptions immediately
Step 3
Independent Practice
10 minutes
- Students solve remaining problems on their own dry-erase boards or scratch paper
- Circulate to offer targeted support and confirm correct regrouping
- Use the timer to challenge sleuths: aim to solve three cases in five minutes
- Students self-check their work against the answer key once finished
Step 4
Reflection & Wrap-Up
5 minutes
- Invite sleuths to share tricky regrouping moments and how they solved them
- Summarize key regrouping strategies and steps
- Highlight real-world relevance: budgeting, shopping, gaming scores
- Assign extra detective cases for homework if needed to reinforce accuracy
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Slide Deck
Subtraction Sleuths Unite
Welcome, subtraction detectives!
Today we’ll master multi-digit subtraction with regrouping by solving real-world mysteries.
Welcome students to the session. Introduce the detective theme and build excitement: “You are all subtraction sleuths on a mission to crack number mysteries!”
Lesson Objective
Students will master multi-digit subtraction with regrouping by solving detective case problems, accurately subtracting 4-digit numbers in contexts like shopping and budgeting.
Read aloud the objective so students know the goal. Emphasize accuracy and real-world connections.
Mystery Case
A shopper budgeted $1,234 but spent $789.
What’s left in the budget?
Pose the mystery scenario: project this slide, then ask: “What’s left in the budget?”
Key Vocabulary
• Minuend – the starting amount (e.g., 1,234)
• Subtrahend – the amount taken away (e.g., 789)
• Difference – the result after subtraction
Introduce key vocabulary and have students repeat each term. Ask volunteers to use them in a sentence.
Regrouping Review
Example: 4,302 − 1,789
- Borrow from the 3 in the hundreds place
- Ten → 12 in the ones column: 12 − 9 = 3
- Hundreds column now 2: 2 − 7 (borrow again)…
Continue until you find the difference: 2,513
Walk through each regrouping step slowly, writing on the board in columns. Highlight when and why we borrow.
Guided Practice #1
Detective Case 1:
3,456 − 2,178
• Set up columns
• Regroup where needed
• Find the difference
Project this problem. Ask a volunteer to show each step on a dry-erase board. Correct errors in real time.
Guided Practice #2
Detective Case 2:
5,021 − 3,647
• Work together on dry-erase boards
• Explain each borrow step aloud
Project the second problem. Invite pairs to solve and share their process.
Independent Practice
Solve these detective subtraction problems on your own:
• 4,890 − 2,736
• 6,004 − 1,589
• 7,215 − 3,478
Self-check with Answer Key for Detective Cases when finished.
Distribute Detective Case Worksheets. Circulate and time students: “Can you solve three cases in five minutes?”
Reflection & Wrap-Up
• Which regrouping step did you find most challenging?
• What strategy helped you the most?
• Real-world relevance: budgeting, shopping, scores
Optional homework: More cases from Detective Case Worksheets.
Lead a brief discussion: ask students to share tricky parts and tips. Reinforce strategies. Assign extra cases for homework if needed.
Worksheet
Detective Case Worksheets
Name: ____________ Date: ____________
Solve each subtraction mystery. Show your work in the space below. When finished, check with the Answer Key for Detective Cases.
- A toy store received 4,567 new action figures. This week they sold 2,389 of them. How many action figures remain?
4,567 − 2,389 = ________
- The bakery made 3,245 muffins before the morning rush. By noon they had sold 1,578. How many muffins are left?
3,245 − 1,578 = ________
- A gamer had a score of 8,004 points but lost 2,736 points in a challenge. What is the current score?
8,004 − 2,736 = ________
- The class budget was $7,500 for supplies. They spent $4,325 on art materials. How much budget remains?
7,500 − 4,325 = ________
- The school fundraiser collected $9,210 but paid $6,895 for event costs. How much money is left?
9,210 − 6,895 = ________
- A charity set a goal of $5,000. They have raised $3,746 so far. How much more do they need to reach the goal?
5,000 − 3,746 = ________
Answer Key
Answer Key for Detective Cases
Refer back to the original problems in Detective Case Worksheets to follow along.
1. 4,567 − 2,389
Step-by-Step Solution:
- Write the numbers in columns:
4 5 6 7
– 2 3 8 9 - Ones place: 7 − 9 → cannot subtract, so borrow 1 ten from the 6 (tens place).
• Tens becomes 5, ones becomes 17.
• 17 − 9 = 8. - Tens place: now 5 − 8 → cannot subtract, so borrow 1 hundred from the 5 (hundreds place).
• Hundreds becomes 4, tens becomes 15.
• 15 − 8 = 7. - Hundreds place: 4 − 3 = 1.
- Thousands place: 4 − 2 = 2.
Answer: 2,178
2. 3,245 − 1,578
Step-by-Step Solution:
- Columns:
3 2 4 5
– 1 5 7 8 - Ones: 5 − 8 → borrow from tens (4→3), ones = 15 → 15 − 8 = 7.
- Tens: 3 − 7 → borrow from hundreds (2→1), tens = 13 → 13 − 7 = 6.
- Hundreds: 1 − 5 → borrow from thousands (3→2), hundreds = 11 → 11 − 5 = 6.
- Thousands: 2 − 1 = 1.
Answer: 1,667
3. 8,004 − 2,736
Step-by-Step Solution:
- Columns:
8 0 0 4
– 2 7 3 6 - Ones: 4 − 6 → borrow from tens (0→needs borrowing):
• Tens (0) borrows from hundreds (0), which borrows from thousands (8→7).
• Hundreds becomes 9 (after lending 1), tens becomes 9, ones becomes 14.
• 14 − 6 = 8. - Tens: 9 − 3 = 6.
- Hundreds: 9 − 7 = 2.
- Thousands: 7 − 2 = 5.
Answer: 5,268
4. 7,500 − 4,325
Step-by-Step Solution:
- Columns:
7 5 0 0
– 4 3 2 5 - Ones: 0 − 5 → borrow from tens (0→needs borrowing):
• Tens borrows from hundreds (5→4), tens = 10→9 after lending, ones = 10.
• 10 − 5 = 5. - Tens: 9 − 2 = 7.
- Hundreds: 4 − 3 = 1.
- Thousands: 7 − 4 = 3.
Answer: 3,175
5. 9,210 − 6,895
Step-by-Step Solution:
- Columns:
9 2 1 0
– 6 8 9 5 - Ones: 0 − 5 → borrow from tens (1→0), ones = 10 → 10 − 5 = 5.
- Tens: 0 − 9 → borrow from hundreds (2→1), tens = 10 → 10 − 9 = 1.
- Hundreds: 1 − 8 → borrow from thousands (9→8), hundreds = 11 → 11 − 8 = 3.
- Thousands: 8 − 6 = 2.
Answer: 2,315
6. 5,000 − 3,746
Step-by-Step Solution:
- Columns:
5 0 0 0
– 3 7 4 6 - Ones: 0 − 6 → borrow chain from tens→hundreds→thousands:
• Thousands (5→4), hundreds becomes 9, tens becomes 9, ones = 10.
• 10 − 6 = 4. - Tens: 9 − 4 = 5.
- Hundreds: 9 − 7 = 2.
- Thousands: 4 − 3 = 1.
Answer: 1,254