[{"id":373,"subject":"数学","grade":"初一","stage":"初中","type":"选择题","content":"某学生在平面直角坐标系中描出点A(2, 3)和点B(5, 7)，然后连接这两点形成一条线段。若该学生想找出这条线段的中点坐标，他应该计算的结果是：","answer":"A","explanation":"求平面直角坐标系中两点所连线段的中点坐标，应使用中点坐标公式：中点坐标 = ((x₁ + x₂) ÷ 2, (y₁ + y₂) ÷ 2)。已知点A(2, 3)和点B(5, 7)，则中点横坐标为 (2 + 5) ÷ 2 = 7 ÷ 2 = 3.5，纵坐标为 (3 + 7) ÷ 2 = 10 ÷ 2 = 5。因此，中点坐标为(3.5, 5)。选项A正确。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 15:49:46","updated_at":"2025-12-30 11:11:27","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[{"id":"A","content":"(3.5, 5)","is_correct":1},{"id":"B","content":"(4, 5)","is_correct":0},{"id":"C","content":"(3, 4.5)","is_correct":0},{"id":"D","content":"(3.5, 4.5)","is_correct":0}]},{"id":468,"subject":"数学","grade":"初一","stage":"小学","type":"选择题","content":"喜欢篮球的人数占总人数的30%","answer":"待完善","explanation":"解析待完善","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 17:53:00","updated_at":"2025-12-30 11:11:27","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[]},{"id":2226,"subject":"数学","grade":"七年级","stage":"初中","type":"填空题","content":"某学生在记录一周气温变化时，发现某天的气温比前一天上升了5℃，记作+5℃。如果第二天的气温又比这一天下降了8℃，那么第二天的气温变化应记作____℃。","answer":"-8","explanation":"根据正负数表示相反意义的量的知识点，气温上升用正数表示，下降则用负数表示。题目中气温下降了8℃，因此应记作-8℃。本题考查学生对正负数在实际情境中应用的理解，符合七年级课程标准要求。","solution_steps":"","common_mistakes":"","learning_suggestions":"","difficulty":"简单","points":1,"is_active":1,"created_at":"2026-01-09 14:27:19","updated_at":"2026-01-09 14:27:19","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[]},{"id":1959,"subject":"数学","grade":"七年级","stage":"初中","type":"选择题","content":"某学生在研究校园内不同区域的温度变化时，记录了某一天中五个时间点的气温数据（单位：℃）：-2.5, 3.1, 0.8, -1.2, 4.6。为了分析当天的气温波动情况，该学生计算了这组数据的极差。请问这组气温数据的极差是多少？","answer":"C","explanation":"本题考查数据的收集、整理与描述中极差的概念与计算。极差是一组数据中最大值与最小值之差。首先找出这组气温数据中的最大值和最小值：数据为 -2.5, 3.1, 0.8, -1.2, 4.6，其中最大值为 4.6，最小值为 -2.5。计算极差：4.6 - (-2.5) = 4.6 + 2.5 = 7.1。因此，正确答案为 C。","solution_steps":"","common_mistakes":"","learning_suggestions":"","difficulty":"中等","points":1,"is_active":1,"created_at":"2026-01-07 14:47:16","updated_at":"2026-01-07 14:47:16","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[{"id":"A","content":"5.8","is_correct":0},{"id":"B","content":"6.1","is_correct":0},{"id":"C","content":"7.1","is_correct":1},{"id":"D","content":"6.8","is_correct":0}]},{"id":855,"subject":"数学","grade":"初一","stage":"初中","type":"填空题","content":"在一次环保知识问卷调查中，某班级共收集了60份有效问卷。其中，了解垃圾分类知识的学生占全班人数的75%，那么不了解垃圾分类知识的学生有____人。","answer":"15","explanation":"全班共有60人，了解垃圾分类知识的学生占75%，则不了解的学生占1 - 75% = 25%。计算25%的60人：60 × 25% = 60 × 0.25 = 15。因此，不了解垃圾分类知识的学生有15人。本题考查百分数在实际数据整理中的应用，属于‘数据的收集、整理与描述’知识点，难度简单，符合七年级学生认知水平。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-30 01:07:39","updated_at":"2025-12-30 11:11:27","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[]},{"id":292,"subject":"数学","grade":"初一","stage":"小学","type":"选择题","content":"众数是85，中位数是85","answer":"答案待完善","explanation":"解析待完善","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 15:32:46","updated_at":"2025-12-30 11:11:27","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[]},{"id":326,"subject":"数学","grade":"初一","stage":"初中","type":"选择题","content":"某学生调查了班级同学最喜欢的运动项目，并将数据整理成如下表格。已知喜欢篮球的人数比喜欢足球的多6人，喜欢乒乓球的人数是喜欢羽毛球的2倍，且总人数为40人。如果喜欢足球的有8人，那么喜欢羽毛球的有多少人？","answer":"B","explanation":"根据题意，喜欢足球的有8人，喜欢篮球的比足球多6人，所以喜欢篮球的有 8 + 6 = 14 人。设喜欢羽毛球的有 x 人，则喜欢乒乓球的有 2x 人。总人数为40人，因此可以列出方程：足球人数 + 篮球人数 + 羽毛球人数 + 乒乓球人数 = 总人数，即 8 + 14 + x + 2x = 40。化简得 22 + 3x = 40，解得 3x = 18，x = 6。所以喜欢羽毛球的有6人，正确答案是B。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 15:38:49","updated_at":"2025-12-30 11:11:27","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[{"id":"A","content":"5人","is_correct":0},{"id":"B","content":"6人","is_correct":1},{"id":"C","content":"7人","is_correct":0},{"id":"D","content":"8人","is_correct":0}]},{"id":285,"subject":"数学","grade":"初一","stage":"初中","type":"选择题","content":"某学生在整理班级同学的课外阅读时间数据时，记录了5名同学每天阅读的分钟数分别为：15、20、25、20、30。这组数据的众数和中位数分别是多少？","answer":"A","explanation":"首先将数据按从小到大的顺序排列：15、20、20、25、30。众数是出现次数最多的数，其中20出现了两次，其他数各出现一次，因此众数是20。中位数是位于中间位置的数，由于共有5个数据，中间位置是第3个数，即20，因此中位数也是20。所以正确答案是A。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 15:31:49","updated_at":"2025-12-30 11:11:27","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[{"id":"A","content":"众数是20，中位数是20","is_correct":1},{"id":"B","content":"众数是20，中位数是25","is_correct":0},{"id":"C","content":"众数是25，中位数是20","is_correct":0},{"id":"D","content":"众数是15，中位数是25","is_correct":0}]},{"id":1941,"subject":"数学","grade":"七年级","stage":"初中","type":"填空题","content":"在平面直角坐标系中，点A(2, 3)和点B(8, 7)是某矩形的两个对角顶点，且该矩形的边分别平行于坐标轴。若该矩形的周长是面积的$\\frac{1}{2}$，则这个矩形的另外两个顶点坐标的横坐标之和为____。","answer":"10","explanation":"由A、B为对角顶点且边平行坐标轴，可得另两点为(2,7)和(8,3)。设长为6，宽为4，周长=20，面积=24。验证20 = 24×½成立。另两点横坐标为2和8，和为10。","solution_steps":"","common_mistakes":"","learning_suggestions":"","difficulty":"困难","points":1,"is_active":1,"created_at":"2026-01-07 14:11:56","updated_at":"2026-01-07 14:11:56","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[]},{"id":851,"subject":"数学","grade":"初一","stage":"小学","type":"填空题","content":"某学生在绘制班级同学最喜爱的课外活动统计图时，将数据整理成如下表格：阅读占20%，运动占35%，音乐占15%，绘画占___%，其余为其他活动。已知喜欢绘画的人数比喜欢音乐的人数多6人，且班级总人数为60人，那么绘画所占的百分比是____。","answer":"25","explanation":"首先，根据题意，班级总人数为60人。喜欢音乐的人占15%，即 60 × 15% = 9 人。喜欢绘画的人数比音乐多6人，所以绘画人数为 9 + 6 = 15 人。那么绘画所占的百分比为 (15 ÷ 60) × 100% = 25%。因此，空白处应填写25。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-30 01:04:52","updated_at":"2025-12-30 11:11:27","sort_order":0,"source":null,"tags":null,"analysis":null,"knowledge_point":null,"difficulty_coefficient":null,"suggested_time":null,"accuracy_rate":null,"usage_count":0,"last_used":null,"view_count":0,"favorite_count":0,"options":[]}]