Question: what year did 45 rpm records come out
[{'answer': '1949', 'provenance': [{'wikipedia_id': '156540', 'title': 'Single (music)', 'start_paragraph_id': 16, 'start_character': 47, 'end_paragraph_id': 16, 'end_character': 51, 'bleu_score': 1.0, 'section': 'Section::::Types of physical singles.:7-inch format.\n'}]}]