Help your students sharpen their mathematical thinking and critical analysis skills with our Calculation Error Detector worksheets. This engaging and purposeful activity encourages students to think like a teacher as they identify, explain, and correct errors in decimal calculations. It’s a brilliant way to deepen understanding, promote reasoning, and reinforce correct computation methods across a range of operations.

Each question presents a worked solution to a decimal operation — but with a deliberate mistake. Students must carefully read the question and answer, spot where the error has occurred, and circle it. Then, they rework the question in the space provided, applying correct strategies to find the accurate answer. This process encourages active thinking and builds awareness of common mistakes, especially with decimal place value and algorithm alignment.

Four differentiated worksheet sets are included: adding and subtracting decimals (1–2 decimal places), adding and subtracting decimals (3 decimal places), multiplying decimals, and dividing decimals. With answer keys provided for each, you can use these sheets for whole-class warm-ups, individual practise, group discussions, or even timed challenges. Whether you’re introducing decimal operations or reviewing them before assessment, this resource supports fluency, accuracy, and problem-solving confidence.

Key Learning Outcomes:

• ✅ Identify and explain errors in decimal addition, subtraction, multiplication, and division
• ✅ Apply correct methods to rework decimal calculations
• ✅ Strengthen understanding of place value and decimal alignment
• ✅ Build confidence in evaluating and justifying solutions
• ✅ Develop reasoning and reflection skills through error analysis

What’s Included:

• 4 worksheet versions:
  • - Adding and Subtracting Decimals (1–2 decimal places)
  • - Adding and Subtracting Decimals (3 decimal places)
  • - Multiplying Decimals
  • - Dividing Decimals
• Each worksheet includes multiple error-based problems with space for working out
• Answer keys included for each version

Materials Needed:

• Printed worksheets (one per student or pair)
• Pencils or pens
• Optional: calculators or decimal manipulatives for support
• Timer (optional for challenge extension)

How to Use:

1. Distribute the worksheet version that matches your current topic or student ability level.
2. Students read each question carefully and examine the provided solution.
3. They circle or highlight where the error occurred in the working or answer.
4. Students rework the question correctly in the blank space provided.
5. Use the answer key to check accuracy and discuss common misconceptions as a class.

Ideas for Classroom Use:

• 💡 Use as a warm-up before a decimals lesson to activate prior knowledge
• 💡 Set up as a maths rotation activity where students work in pairs to discuss errors
• 💡 Use as an assessment tool to check conceptual understanding before a unit ends
• 💡 Challenge students to create their own error-based questions for a peer to solve
• 💡 Add a time limit for an exciting revision competition

Top Teacher Tips:

• 💛 Encourage students to explain their corrections using decimal vocabulary
• 💛 Provide scaffolds like number lines or place value charts for students needing support
• 💛 Differentiate by assigning the 1–2 decimal place sheet to consolidate skills before progressing
• 💛 Highlight patterns in errors to guide future teaching and mini-lessons

Calculation Error Detector is a powerful tool for building accuracy, confidence, and deep mathematical thinking. With targeted practise across decimal operations and a focus on reflection and strategy, this resource supports learners at all levels to think critically and compute confidently.