Solve Subtraction Problems

Overview

In this 30-minute lesson, students use subtraction to solve real-world “how many are left?” and comparison problems. They connect concrete counters, bar models, and equations, building on prior work with place value and the meaning of subtraction.

Learning intentions

Students will be able to:

• Use subtraction to solve a real-world problem.
• Identify the starting amount and the amount removed or compared.
• Represent a problem with counters, a bar model, and an equation.
• Explain what the difference means in context.

Success criteria

• I can identify the starting amount.
• I can identify what is removed or compared.
• I can choose addition or subtraction and solve.
• I can write a number sentence and explain my answer.

Curriculum links

• Measurement and Data — solve real-world problems using the four operations, including comparison situations and diagrams.
• Measurement and Data — represent quantities and relationships using visual models.
• Number and Operations in Base Ten — read, write, compare, and calculate with multi-digit whole numbers.
• Mathematical practice — make sense of problems, model with mathematics, and explain reasoning.

Lesson structure (30 minutes)

1. 0–4 min · Hook and vocabulary. Open with the subtraction story introduction and display a picture of 40 apples, asking, “If 12 apples are eaten, how many are left?” Read the problem aloud, briefly review difference, left, fewer, how many more, compare, and equation, and have students turn and say whether the answer should be greater or less than 40. Students use a quiet think, pair, share routine and show thumbs up for subtraction or thumbs down for addition.

2. 4–11 min · I Do: model a take-away story. Use counters to model 40 apples, physically move 12 away, and draw a bar model labeled 40 (whole), 12 (removed), and? (left); connect it to the equation 40 − 12 = 28. Keep symbols large, separate each part of the problem visually, and read every label aloud. Students help count the remaining counters, identify the starting amount and removed amount, and explain why subtraction fits.

3. 11–17 min · We Do: compare and choose an operation. Use the counters and comparison slides to show pairs of quantities, such as 35 and 20, and ask, “How many more?” Model both the bar model and the missing-part equation 20 +? = 35, then connect this to 35 − 20 = 15; present two operation choices and discuss why subtraction finds the difference. Students move virtual counters on the smartboard when called, select addition or subtraction, and justify their choice using the sentence frame, “I chose ___ because the problem asks ___.”

4. 17–25 min · You Do: picture-supported practice. Distribute the picture-supported subtraction worksheet. Students solve the main picture story independently, drawing or using counters if needed, then write a number sentence and explain what the answer means; circulate and ask, “What is the starting amount?” and “What was removed or compared?” Students may respond by writing, pointing to an operation, drawing a bar model, or explaining orally to the teacher or partner.

5. 25–30 min · Check and exit assessment. Return to the review and exit-question slides. Read the five questions aloud, display one question at a time, and have students answer individually using A, B, or C cards or by circling on the worksheet; briefly correct misconceptions after each item. Students complete: 40 − 12 (28, 32, or 52); 50 − 20 (20, 30, or 70); “How many are left?” means add, subtract, or multiply; 35 is how many more than 20 (10, 15, or 55); and 1,000 − 300 (700, 800, or 1,300).

Resources

• the subtraction story and review deck
• the picture-supported subtraction worksheet
• Counters or linking cubes, at least 40 per student or pair
• Smartboard or interactive display
• Large chart paper or whiteboard
• Markers and pencils
• A, B, and C response cards
• Enlarged operation and comparison symbols

Assessment

• During modeling, check whether students can identify the whole, the removed part, and the unknown part of a bar model.
• During guided and independent work, listen for accurate use of left, fewer, how many more, and difference, and check that the equation matches the story.
• Use the five-question exit assessment to identify errors with take-away subtraction, comparison subtraction, and subtracting hundreds from 1,000. Record whether each student solved independently, with a model, or orally.

Differentiation

• Support students with counters, bar models, picture stories, a visible step sequence—identify the starting amount, identify what changed, choose an operation, solve, and explain—and only two operation choices at a time.
• Provide a sentence frame: “There were ___. ___ were removed/compared. I used __ because __. The answer is ___.”
• For dyslexic students and developing readers, read all text aloud, use a clear sans-serif font, enlarge numerals and operation symbols, keep one problem per section, use high-contrast visuals, and separate answer choices with generous spacing.
• Allow oral, pointing, drawing, or manipulatives-based responses. Pair students strategically for discussion while requiring each student to show or explain their own reasoning.