[{"id":190,"subject":"数学","grade":"初一","stage":"初中","type":"选择题","content":"下列运算中，正确的是（ ）。","answer":"D","explanation":"本题考查的是七年级整式加减中的同类项合并。同类项是指所含字母相同，并且相同字母的指数也相同的项，只有同类项才能合并。选项A中，3a和2b不是同类项，不能合并，错误；选项B中，5y² - 2y² = 3y²，而不是3，漏掉了字母部分，错误；选项C中，4x²y和5xy²所含字母的指数不同（x和y的次数不对应），不是同类项，不能合并，错误；选项D中，7mn和3nm是同类项（因为mn = nm），可以合并，7mn - 3nm = 7mn - 3mn = 4mn，正确。因此，正确答案是D。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 14:02:14","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":"3a + 2b = 5ab","is_correct":0},{"id":"B","content":"5y² - 2y² = 3","is_correct":0},{"id":"C","content":"4x²y - 5xy² = -x²y","is_correct":0},{"id":"D","content":"7mn - 3nm = 4mn","is_correct":1}]},{"id":2286,"subject":"数学","grade":"七年级","stage":"初中","type":"填空题","content":"在数轴上，点A表示的数是-3，点B与点A之间的距离是7个单位长度，且点B在原点右侧，则点B表示的数是____。","answer":"4","explanation":"点A表示-3，点B与点A相距7个单位长度，且在原点右侧。从-3向右移动7个单位，即计算 -3 + 7 = 4。因此点B表示的数是4。","solution_steps":"","common_mistakes":"","learning_suggestions":"","difficulty":"简单","points":1,"is_active":1,"created_at":"2026-01-09 16:27:46","updated_at":"2026-01-09 16:27:46","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":316,"subject":"数学","grade":"初一","stage":"小学","type":"选择题","content":"7人","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 15:36:30","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":273,"subject":"数学","grade":"初一","stage":"初中","type":"选择题","content":"在一次班级调查中，某学生记录了10名同学的身高（单位：厘米）：150，152，155，155，158，160，162，165，168，170。这组数据的中位数是多少？","answer":"C","explanation":"中位数是将一组数据从小到大排列后，处于中间位置的数。本题共有10个数据，是偶数个，因此中位数是第5个和第6个数据的平均数。数据已按顺序排列：150，152，155，155，158，160，162，165，168，170。第5个数是158，第6个数是160。中位数为（158 + 160）÷ 2 = 318 ÷ 2 = 159。因此正确答案是C。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 15:30:20","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":"155","is_correct":0},{"id":"B","content":"158","is_correct":0},{"id":"C","content":"159","is_correct":1},{"id":"D","content":"160","is_correct":0}]},{"id":510,"subject":"数学","grade":"初一","stage":"初中","type":"选择题","content":"某学生在整理班级同学最喜欢的课外活动调查数据时，将结果绘制成扇形统计图。已知喜欢阅读的同学所占圆心角为72度，喜欢运动的同学所占圆心角为108度，喜欢绘画的同学所占圆心角为60度，其余同学喜欢音乐。如果全班共有60人，那么喜欢音乐的同学有多少人？","answer":"B","explanation":"扇形统计图中，整个圆代表全班人数，圆心角总和为360度。已知阅读、运动、绘画对应的圆心角分别为72度、108度、60度，三者之和为72 + 108 + 60 = 240度。因此，喜欢音乐的同学所占圆心角为360 - 240 = 120度。由于圆心角与人数成正比，可列比例计算：120 ÷ 360 = 1\/3，所以喜欢音乐的人数为60 × (1\/3) = 20人。故正确答案为B。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 18:15:29","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":"18人","is_correct":0},{"id":"B","content":"20人","is_correct":1},{"id":"C","content":"22人","is_correct":0},{"id":"D","content":"24人","is_correct":0}]},{"id":1055,"subject":"数学","grade":"初一","stage":"初中","type":"填空题","content":"在一次班级大扫除中，某学生负责统计同学们带来的清洁工具数量。他记录了5位同学带来的抹布数量分别为：3块、5块、4块、6块、2块。这5位同学平均每人带来____块抹布。","answer":"4","explanation":"要计算平均数，需将所有数据相加后除以数据的个数。计算过程为：(3 + 5 + 4 + 6 + 2) ÷ 5 = 20 ÷ 5 = 4。因此，平均每人带来4块抹布。本题考查的是数据的收集、整理与描述中的平均数计算，属于七年级数学课程内容，难度简单，情境贴近学生生活。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-30 06:42:25","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":453,"subject":"数学","grade":"初一","stage":"初中","type":"选择题","content":"某班级为了了解学生每天完成数学作业所用的时间，随机抽取了10名学生进行调查，得到的数据如下（单位：分钟）：25, 30, 35, 20, 40, 30, 25, 35, 30, 45。这组数据的众数是多少？","answer":"B","explanation":"众数是一组数据中出现次数最多的数。观察数据：25出现2次，30出现3次，35出现2次，20、40、45各出现1次。因此，30是出现次数最多的数，所以这组数据的众数是30。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 17:45:43","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":"25","is_correct":0},{"id":"B","content":"30","is_correct":1},{"id":"C","content":"35","is_correct":0},{"id":"D","content":"40","is_correct":0}]},{"id":2468,"subject":"数学","grade":"八年级","stage":"初中","type":"解答题","content":"如图，在平面直角坐标系中，点A(0, 4)，点B(6, 0)，点C为线段AB上的一个动点。以AC为边作正方形ACDE，使得点D在x轴上方，点E在点A的右侧。连接BE，交y轴于点F。已知正方形ACDE的面积为S，线段OF的长度为y（O为坐标原点）。\\n\\n(1) 设AC = x，试用含x的代数式表示S，并求出S的取值范围；\\n(2) 当点C在线段AB上运动时，求y关于x的函数关系式，并指出该函数的定义域；\\n(3) 若某学生测得三组数据如下：当x = 2时，y ≈ 1.6；当x = 3时，y ≈ 2.4；当x = 4时，y ≈ 3.2。请判断该学生记录的数据是否符合你求得的函数关系，并说明理由。","answer":"待完善","explanation":"解析待完善","solution_steps":"待完善","common_mistakes":"","learning_suggestions":"","difficulty":"中等","points":1,"is_active":1,"created_at":"2026-01-10 14:32:33","updated_at":"2026-01-10 14:32:33","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":1936,"subject":"数学","grade":"七年级","stage":"初中","type":"填空题","content":"某学生在平面直角坐标系中绘制了一个等腰三角形ABC，顶点A的坐标为(2, 5)，底边BC的两个端点B和C分别位于x轴上，且关于直线x = 2对称。若三角形ABC的面积为12，则点B的横坐标为____。","answer":"-1","explanation":"设B(2-a,0)，C(2+a,0)，则底边BC=2a，高为5。由面积公式½×2a×5=15，得a=3，故B横坐标为2-3=-1。","solution_steps":"","common_mistakes":"","learning_suggestions":"","difficulty":"困难","points":1,"is_active":1,"created_at":"2026-01-07 14:10:52","updated_at":"2026-01-07 14:10:52","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":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":[]}]