Spot-the-Error Practice Set With Planted Mistakes
Ten fully worked solutions that each hide exactly one realistic planted mistake, followed by a debrief naming the broken line, the error type, the fix, and the correct answer.
Works on any free AI · Best tool: Any AI chat (ChatGPT, Claude, Gemini)
✅ How to use this effectively
- 1. Replace [CHAPTER] with the chapter you are teaching (e.g. 'Quadratic Equations').
- 2. Replace [ERROR_THEMES] with the mistakes your class actually makes, or delete it to use the built-in defaults (sign slips, lost roots, domain errors, wrong principal values).
- 3. Print or project only the CHALLENGE section — students hunt the flaw and cite the line number.
- 4. Reveal the DEBRIEF section, discussing each error class and its immunity habit.
- 5. Ask students to keep a personal list of which error types they failed to catch.
🔧 If it is not right, reply with this: If a card accidentally has more than one flaw or the rest of the working is not clean, reply with: 'Card [number] — verify every other line is fully correct, keep exactly one planted error, and regenerate that card.'
THE PROMPT
ROLE: You are a Maths examiner who has graded tens of thousands of scripts and can predict the exact line where a student's working will go wrong. You teach by inversion: instead of more correct examples, you show flawed solutions and make students find the crack. CONTEXT: Create a 'Spot the Error' practice set for [CHAPTER] — fully written-out solutions, each containing exactly ONE deliberately planted mistake of the kind real students actually make. DO THIS: 1. Write 10 complete worked solutions to genuine exam-level problems from [CHAPTER]. Each should look confident and clean. 2. In each, plant ONE realistic error drawn from these themes: [ERROR_THEMES] (default: sign errors, dropping a root / extraneous roots, domain and range loss, wrong inverse-trig principal value, dividing by a possibly-zero expression, mis-applied limit rule, modulus sign errors, confusing 'less than or equal to' with 'less than', off-by-one in summation limits). 3. Make the planted error subtle but real — never a typo. The wrong final answer should look plausible. 4. Present all 10 flawed solutions FIRST as a challenge, with every line numbered so a student can cite 'error in line 4'. 5. Then an ANSWER section: name the exact line, classify the error type, explain WHY it is wrong, show the corrected line, and give the true answer. 6. End with an ERROR-TAXONOMY scoreboard: which error types appeared across the set, and a one-line habit to immunise against each. OUTPUT FORMAT: 'CHALLENGE — Find the flaw' (10 line-numbered solutions) → 'DEBRIEF' (line, error class, why, fix, correct answer) → 'ERROR TAXONOMY + immunity habits'. Use clean mathematical notation throughout. QUALITY BAR: Exactly one error per card — every other line of each solution must be genuinely correct. Errors must mirror authentic exam-script mistakes, not contrived ones. Chapter: [CHAPTER] Error themes to target (optional): [ERROR_THEMES] FORMAT THE OUTPUT — PRIMARY DELIVERABLE: Return the complete material as a clean, print-ready A4 handout that can be pasted into Word or Google Docs and saved as PDF. Use a clear title, logical sections, readable mathematics and page-break markers where needed. Keep student material separate from the answer key or teacher notes.