[{"id": 1, "type": "short_answer", "skill": "addition", "question": "Calculate: 30 + 42", "difficulty": "medium", "explanation": "Add by place value, regrouping as needed.", "needs_review": false, "correct_answer": "72"}, {"id": 2, "type": "multiple_choice", "skill": "addition", "options": ["71", "82", "77", "72"], "question": "What is the sum of 30 and 42?", "difficulty": "easy", "explanation": "30+42=72", "needs_review": false, "correct_answer": "72"}, {"id": 3, "type": "true_false", "skill": "properties", "question": "The commutative property means 30+42 = 42+30.", "difficulty": "easy", "explanation": "The commutative property states changing the order of addends does not change the sum.", "needs_review": false, "correct_answer": "True"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 15 × 3", "difficulty": "medium", "explanation": "Multiply: 15×3=45", "needs_review": false, "correct_answer": "45"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 4 × 10", "difficulty": "medium", "explanation": "Multiply: 4×10=40", "needs_review": false, "correct_answer": "40"}]