Decimal Operations—Error Analysis (B)

Sep 23, 2026

Uploaded by Fahsai

Decimal Operations—Error Analysis (B) is a set of K-12 math practice problems where students correct mistakes made in decimal addition, subtraction, multiplication, and division. Each item shows a student's incorrect work, then prompts learners to identify the error and provide the correct result. Common misconceptions are targeted, including aligning decimal points, proper decimal placement after multiplying, and adjusting numbers when dividing by a decimal. An answer key supplies the correct solutions and explanations.

LanguageEnglish

CategoryExam

FormatPDF

Pages3

Reading Time8 min

AccessFree to download

Directions

Common error reminders

Practice problems (Student work with mistakes)

1. 7.5 + 2.35

2. 4 − 1.37

3. 2.4 × 5

4. 0.36 ÷ 0.4

5. 6.4 + 0.85

6. 3.04 − 1.78

7. 1.5 × 0.4

8. 7.2 ÷ 8

Challenge Problem: 0.6 × 0.4

Answer Key

Name: ______________________________________ Decimal Operations—Error Analysis (B) Directions: Each problem below shows a student's work that contains an error. Find the mistake, explain it, and show the correct solution. Remember: Common errors: not aligning decimal points when adding or subtracting, incorrect decimal placement when multiplying, not adjusting both numbers when dividing by a decimal. 1. 7.5 + 2.35 Student's work: 7.5 + 2.35 → 75 + 235 = 310 → answer: 3.10 What is the mistake? _______________________________________________ Correct answer: 2. 4 − 1.37 Student's work: 4 − 1.37 → 3.37 What is the mistake? _______________________________________________ Correct answer: 3. 2.4 × 5 Student's work: 24 × 5 = 120, → answer: 1.20 What is the mistake? Correct answer: 4. 0.36 ÷ 0.4 Student's work: 0.36 ÷ 0.4 → answer: 0.09 What is the mistake? _______________________________________________ Correct answer: Mashup Math LLC | Al[l Rights Reserved | Get More K-12 Math Worksheets at www.mashupmath.com](l Rights Reserved | Get More K-12 Math Worksheets at www.mashupmath.com) 5. 6.4 + 0.85 Student's work: 6.4 + 0.85 → 64 + 85 = 149 → answer: 1.49 What is the mistake? Correct answer: 6. 3.04 − 1.78 Student's work: 3.04 − 1.78 → answer: 2.74 What is the mistake? Correct answer: 7. 1.5 × 0.4 Student's work: 15 × 4 = 60 → answer: 6.0 What is the mistake? Correct answer: 8. 7.2 ÷ 8 Student's work: 72 ÷ 8 = 9, so 7.2 ÷ 8 = 9 What is the mistake? Correct answer: Challenge Problem A student solved 0.6 × 0.4 and got 2.4. Student's work: 0.6 × 0.4 → 6 × 4 = 24→ answer: 2.4 a) What mistake did the student make? b) Show the correct solution. Mashup Math LLC | Al[l Rights Reserved | Get More K-12 Math Worksheets at www.mashupmath.com](l Rights Reserved | Get More K-12 Math Worksheets at www.mashupmath.com) ANSWER KEY 1.) 7.5 + 2.35 = 9.85 | Error: Decimal points were not aligned. 7.50 + 2.35 = 9.85. 2.) 4 − 1.37 = 2.63 | Error: 4 must be written as 4.00 before subtracting. 4.00 − 1.37 = 2.63. 3.) 2.4 × 5 = 12 | Error: 2.4 has 1 decimal place; 5 has 0. Total: 1. 120 → 12.0 = 12. 4.) 0.36 ÷ 0.4 = 0.9 | Error: Multiply BOTH by 10: 3.6 ÷ 4 = 0.9. Move the decimal RIGHT to eliminate it from the divisor. 5.) 6.4 + 0.85 = 7.25 | Error: Decimal points were not aligned. 6.40 + 0.85 = 7.25. 6.) 3.04 − 1.78 = 1.26 | Error: You must borrow, not flip. 3.04 − 1.78 = 1.26. 7.) 1.5 × 0.4 = 0.6 | Error: 1.5 has 1 decimal place, 0.4 has 1 → total 2. 60 → 0.60 = 0.6. 8.) 7.2 ÷ 8 = 0.9 | Error: The decimal point in the quotient goes directly above the decimal in the dividend. 7.2 ÷ 8 = 0.9. 9.) Challenge Problem: a) Placed 1 decimal place instead of 2. (0 .6 has 1, 0.4 has 1 → total 2 decimal places) b) 0.24 (24 → 0 .24) Mashup Math LLC | Al[l Rights Reserved | Get More K-12 Math Worksheets at www.mashupmath.com](l Rights Reserved | Get More K-12 Math Worksheets at www.mashupmath.com)

FAQs

What does each problem require students to do?

Each problem provides a student's incorrect work. Students must find the mistake, explain it, and write the correct solution.

What are the most common decimal errors this worksheet focuses on?

It emphasizes aligning decimal points for addition and subtraction, placing the decimal correctly for multiplication, and adjusting both numbers when dividing by a decimal.

How is the challenge problem different from the standard problems?

The challenge problem asks for the specific mistake made in multiplying 0.6 × 0.4 and then requires showing the correct solution.

Sep 23, 2026

Uploaded by Fahsai

Decimal Operations—Error Analysis (B)_Page 1

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