[{"id": 1, "type": "short_answer", "skill": "area", "question": "Find the area of a rectangle: length=5, width=4", "difficulty": "medium", "explanation": "A=l×w=5×4=20 sq units.", "needs_review": false, "correct_answer": "20"}, {"id": 2, "type": "multiple_choice", "skill": "perimeter", "options": ["18", "20", "9", "20"], "question": "Find the perimeter of a rectangle: length=5, width=4", "difficulty": "medium", "explanation": "P=2(l+w)=2(5+4)=2(9)=18", "needs_review": false, "correct_answer": "18"}, {"id": 3, "type": "short_answer", "skill": "computation", "question": "Calculate: 15 × 19", "difficulty": "medium", "explanation": "Multiply: 15×19=285", "needs_review": false, "correct_answer": "285"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 4 × 16", "difficulty": "medium", "explanation": "Multiply: 4×16=64", "needs_review": false, "correct_answer": "64"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 4 × 16", "difficulty": "medium", "explanation": "Multiply: 4×16=64", "needs_review": false, "correct_answer": "64"}]