Common Mistakes
Learn
Even good math students make mistakes with division. Learning about common errors helps you avoid them!
Mistake 1: Forgetting to bring down digits
When doing long division, always remember to bring down the next digit after subtracting.
Mistake 2: Putting digits in the wrong place
Each digit in your answer must be directly above the digit you are working with in the dividend.
Mistake 3: Forgetting zeros in the quotient
If the divisor does not go into a number, you must write 0 in the quotient and bring down the next digit.
Mistake 4: Subtraction errors
Double-check your subtraction at each step. One small error can make your whole answer wrong.
Mistake 5: Not checking your answer
Always multiply your answer by the divisor to verify. Quotient x Divisor = Dividend (plus remainder, if any).
Examples
Can you spot what went wrong in these examples?
Example 1: Spot the error
Student work: 504 divided by 4 = 16
The mistake: The student forgot to write a 0 in the quotient. 4 goes into 5 once, with 1 left over. Bring down 0 to make 10. 4 goes into 10 twice. Bring down 4 to make 24. 4 goes into 24 six times.
Correct answer: 126
Example 2: Spot the error
Student work: 234 divided by 6 = 49
The mistake: Subtraction error. 6 goes into 23 three times (18). 23 - 18 = 5 (not 4). Bring down 4 to make 54. 6 goes into 54 nine times.
Correct answer: 39
Practice
For each question, find the correct answer and identify what mistake might have been made. Click to reveal the answer.
Question 1: What is 408 divided by 4? (A student got 12. What was the mistake?)
Answer: 102
The student forgot to include the 0 in the middle. 4 goes into 4 once, into 0 zero times, and into 8 twice. The answer is 102, not 12.
Question 2: What is 315 divided by 5?
Answer: 63
5 goes into 31 six times (30), subtract to get 1, bring down 5 to make 15. 5 goes into 15 three times.
Question 3: What is 720 divided by 8?
Answer: 90
8 goes into 72 nine times (72), subtract to get 0, bring down 0. 8 goes into 0 zero times. Answer: 90.
Question 4: What is 612 divided by 6? (A student got 12. What was the mistake?)
Answer: 102
The student skipped the 0. 6 goes into 6 once, into 1 zero times (write 0!), bring down 2 to make 12. 6 goes into 12 twice. Answer: 102.
Question 5: What is 549 divided by 9?
Answer: 61
9 goes into 54 six times (54), subtract to get 0, bring down 9. 9 goes into 9 once. Answer: 61.
Question 6: What is 805 divided by 5?
Answer: 161
5 goes into 8 once (5), subtract to get 3, bring down 0 to make 30. 5 goes into 30 six times. Bring down 5. 5 goes into 5 once. Answer: 161.
Question 7: Check this work: 392 divided by 7 = 56. Is it correct?
Answer: Yes, it is correct!
Check: 56 x 7 = 392. The answer is correct.
Question 8: Check this work: 456 divided by 8 = 67. Is it correct?
Answer: No, it is incorrect!
Check: 67 x 8 = 536, not 456. The correct answer is 57 (57 x 8 = 456).
Question 9: What is 903 divided by 3?
Answer: 301
3 goes into 9 three times, into 0 zero times (write 0!), into 3 once. Answer: 301.
Question 10: What is 4,824 divided by 8?
Answer: 603
8 goes into 48 six times (48), subtract to get 0, bring down 2. 8 goes into 2 zero times (write 0!), bring down 4 to make 24. 8 goes into 24 three times. Answer: 603.
Check Your Understanding
Remember these tips to avoid common mistakes:
- Always write a 0 in the quotient when the divisor does not go into a number.
- Double-check your subtraction at every step.
- Verify your answer by multiplying: Quotient x Divisor should equal the Dividend.
Next Steps
- Review any concepts that felt challenging
- Move on to the next lesson when ready
- Return to practice problems periodically for review