[{"id": 1, "type": "short_answer", "skill": "addition", "question": "Calculate: 37 + 21", "difficulty": "medium", "explanation": "Add by place value, regrouping as needed.", "needs_review": false, "correct_answer": "58"}, {"id": 2, "type": "multiple_choice", "skill": "addition", "options": ["68", "63", "57", "58"], "question": "What is the sum of 37 and 21?", "difficulty": "easy", "explanation": "37+21=58", "needs_review": false, "correct_answer": "58"}, {"id": 3, "type": "true_false", "skill": "properties", "question": "The commutative property means 37+21 = 21+37.", "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: 16 × 4", "difficulty": "medium", "explanation": "Multiply: 16×4=64", "needs_review": false, "correct_answer": "64"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 13 × 18", "difficulty": "medium", "explanation": "Multiply: 13×18=234", "needs_review": false, "correct_answer": "234"}, {"id": 6, "type": "short_answer", "skill": "computation", "question": "Calculate: 9 × 18", "difficulty": "medium", "explanation": "Multiply: 9×18=162", "needs_review": false, "correct_answer": "162"}, {"id": 7, "type": "short_answer", "skill": "computation", "question": "Calculate: 5 × 20", "difficulty": "medium", "explanation": "Multiply: 5×20=100", "needs_review": false, "correct_answer": "100"}, {"id": 8, "type": "short_answer", "skill": "computation", "question": "Calculate: 6 × 7", "difficulty": "medium", "explanation": "Multiply: 6×7=42", "needs_review": false, "correct_answer": "42"}, {"id": 9, "type": "short_answer", "skill": "computation", "question": "Calculate: 6 × 20", "difficulty": "medium", "explanation": "Multiply: 6×20=120", "needs_review": false, "correct_answer": "120"}, {"id": 10, "type": "short_answer", "skill": "computation", "question": "Calculate: 9 × 12", "difficulty": "medium", "explanation": "Multiply: 9×12=108", "needs_review": false, "correct_answer": "108"}, {"id": 11, "type": "short_answer", "skill": "computation", "question": "Calculate: 6 × 8", "difficulty": "medium", "explanation": "Multiply: 6×8=48", "needs_review": false, "correct_answer": "48"}, {"id": 12, "type": "short_answer", "skill": "computation", "question": "Calculate: 15 × 7", "difficulty": "medium", "explanation": "Multiply: 15×7=105", "needs_review": false, "correct_answer": "105"}]