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Error-Checking Templates
Error-Checking Templates
Course: Abacus for Children — Levels 2–3
4 pages of worked problems with deliberate errors. Find and correct each mistake. 20 problems.
Abacus Progress Pack — Error Checking Templates
20 problems across 4 pages. Each problem shows a worked solution that may contain a deliberate error. Your job: find the error (if any), explain what went wrong, and write the correct answer.
Important: Some problems are actually correct! You must decide whether each one has an error or not.
Page 1 of 4 — 5-Complement Errors
Student's work
Push 3 lower beads up. Then push 3 more lower beads up.
Student's answer: 6
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Push 4 lower beads up. Use 5-rule: push upper bead down, remove 3 lower beads.
Student's answer: 6
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Push 4 lower beads up. Use 5-rule: push upper bead down, remove 2 lower beads.
Student's answer: 7
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Show 6 (upper bead down + 1 lower bead). Remove 3 lower beads.
Student's answer: 3
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Show 8 (upper bead down + 3 lower beads). Use 5-rule: push upper bead up, add 2 lower beads.
Student's answer: 5
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Page 2 of 4 — 10-Complement Errors
Student's work
Show 9. Use 10-rule: carry 1 to tens, remove 4 from ones.
Student's answer: 15
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Show 8. Use 10-rule: carry 1 to tens, remove 7 from ones.
Student's answer: 18
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Show 7. Use 10-rule: carry 1 to tens, remove 6 from ones.
Student's answer: 11
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Show 11. Cannot remove 7 from ones (only 1 there). Borrow from tens: remove 1 ten, add 3 to ones.
Student's answer: 4
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Show 14. Borrow from tens: remove 1 ten, add 8 to ones.
Student's answer: 12
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Page 3 of 4 — Carry/Borrow Chain Errors
Student's work
Ones: 8+5=13, write 3, carry 1. Tens: 2+1=3, plus carry 1=4. Answer: 43.
Student's answer: 43
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Ones: 7+6=13, write 3, carry 1. Tens: 4+3=7 (forgot to add carry).
Student's answer: 73
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Ones: 3-8 cannot do, borrow from tens. Tens becomes 4. Ones: 13-8=5. Tens: 4-2=2.
Student's answer: 25
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Ones: 2-5 cannot, borrow. Tens becomes 5. Ones: 12-5=7. Tens: 6-3=3.
Student's answer: 37
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Ones: 5+7=12, write 2, carry 1. Tens: 0+9=9, plus carry=10, write 0, carry 1. Hundreds: 1+0=1.
Student's answer: 102
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Page 4 of 4 — Mixed Complex Errors
Student's work
Show 7. 5-complement of 4 is 1. Push upper bead down, remove 1 lower bead.
Student's answer: 11
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Ones: 6+7=13, write 3, carry 1. Tens: 5+8=13, plus carry=14, write 4, carry 1. Hundreds: 1+1=2.
Student's answer: 243
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Ones: 0-6, borrow from tens. Tens is 0 too, so borrow from hundreds. Hundreds: 1. Tens: 9 (after cascading borrow). Ones: 10-6=4. Tens: 9-8=1.
Student's answer: 114
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Ones: 3+9=12, write 2, carry 1. Tens: 7+4=11, write 1, carry 1.
Student's answer: 112
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Student's work
Ones: 4-8, borrow from tens. Tens is 0, cascade borrow from hundreds. H:2, T:9, O:14. O: 14-8=6. T: 9-5=4. H: 2-1=1.
Student's answer: 146
Is there an error? (Circle one): YES / NO
If YES, what went wrong?
What rule was violated?
Correct answer:
Score
18+ = Excellent · 14-17 = Good · below 14 = Review error types carefully
Parent tip
Error-checking builds meta-cognitive skills — the ability to monitor one's own thinking. Discuss each error with your child: what rule was used, what rule should have been used, and how to recognise the mistake in future. The problems marked “correct” build the habit of confirming right answers too.
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