Decimal Subtraction Mastery

Grade Level

6th Grade Special Education Resource Class

Time

20 minutes

Class Size

9 students

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Common Core Alignment

CCSS.MATH.CONTENT.5.NBT.B.7
Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

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Learning Objectives

By the end of the lesson, students will be able to:

• Understand and visually model the subtraction of decimals from whole numbers using base-ten blocks or decimal grids.
• Apply place value knowledge and the borrowing process to solve decimal subtraction problems accurately.
• Confidently write and solve decimal subtraction problems in abstract form after hands-on practice.
• Collaborate in pairs to reinforce learning through peer discussion.

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Materials Needed

• Base-ten blocks (units, rods, flats) or printable decimal grids (clearly marked in tenths and thousandths)
• Whiteboards and dry erase markers for each pair
• Dyslexia-friendly subtraction problem sheets (using sans-serif fonts like OpenDyslexic and color-coded decimal places)
• Visual step-by-step subtraction anchor chart (large, mounted, or projected)
• Timer

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Lesson Schedule

1. Warm-Up and Review (3 minutes)

• Briefly review place value concepts focusing on whole numbers and decimals to thousandths.
• Use a quick oral Q&A: “What place is the 3 in 0.003?” “How many tenths make a whole?”
• Show a whole number on base-ten blocks (e.g., 7 flats = 7) as a refresher.

Differentiation: Use multisensory cues — tap cubes while counting, highlight decimals visually.

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2. Modeling Subtraction with Visuals (7 minutes)

• Introduce the problem "7 - 0.003".
• Demonstrate with base-ten blocks:
  • Show 7 flats (whole units).
  • Explain that 0.003 means 3 thousandths blocks (smallest units).
  • Since there are no thousandths in 7, guide them through borrowing by exchanging 1 flat for 10 rods, then 1 rod for 10 units, and finally 1 unit for 10 thousandths blocks.
• Parallel display of decimal grids to show this conversion visually.
• Write out the subtraction problem vertically as it's modeled.
• Emphasize the borrowing process step-by-step alongside the blocks/grids.
• Encourage students to verbalize the process to reinforce understanding.

Differentiation:

• For students struggling with language, pair verbal explanations with clear visual cues and gestures.
• Use color-coded borrowing steps to reduce working memory load.
• Anchor chart remains visible to guide students.

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3. Paired Practice with Guided Support (8 minutes)

• Students pair up (3 pairs + 3 individual supports if needed).
• Each pair receives a set of dyslexia-friendly subtraction problems similar to "5 - 0.006" or "8 - 0.004".
• Students use base-ten blocks or decimal grids to model, then solve the problem on whiteboards.
• Teacher circulates, providing scaffolded questioning:
  • “What place do you borrow from?”
  • “How many thousandths did you get after borrowing?”
  • “Can you write the subtraction vertically from your model?”
• Encourage peer coaching: pairs explain steps to each other aloud.

Differentiation:

• Provide extra manipulatives for tactile learners.
• Use sentence starters for those who struggle to explain (“First, I borrowed...”).
• Allow use of whisper phones or quiet reading areas for processing.

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4. Wrap-Up and Quick Assessment (2 minutes)

• Call on volunteers to demonstrate solution from one pair’s problem, either with blocks or on whiteboard.
• Summarize key steps: place value awareness, borrowing, and connecting model to written form.
• Assessment: Students write one subtraction problem of their own choice and model it using blocks or grids, then explain their solution verbally or in writing.

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Special Notes

• Use consistent vocabulary: "thousandths," "borrow," "place value," "exchange."
• Provide positive reinforcement focusing on effort and process, not only correct answers.
• Use accessible fonts and avoid clutter on materials to reduce distractions.
• Keep instructions short, clear, and repeated when necessary.

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Extension Idea (if time permits or follow-up lesson)

• Introduce decimal subtraction where decimals subtract decimals, building on the understanding of borrowing with base-ten blocks.

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This detailed, multisensory approach is designed to meet the needs of diverse learners in your resource classroom while strictly aligning with Common Core standards to build solid conceptual understanding and procedural fluency with decimal subtraction.