习题练习

[{"id":560,"subject":"数学","grade":"初一","stage":"小学","type":"选择题","content":"102千克","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 19:22:34","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":324,"subject":"数学","grade":"初一","stage":"小学","type":"选择题","content":"某学生在整理班级同学的课外阅读时间（单位：小时）时，记录了以下数据：2，3，5，3，4，3，6。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：2，3，5，3，4，3，6。其中数字2出现1次，3出现3次，4出现1次，5出现1次，6出现1次。因此，出现次数最多的是3，共出现3次。所以这组数据的众数是3。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 15:38:21","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":"2","is_correct":0},{"id":"B","content":"3","is_correct":1},{"id":"C","content":"4","is_correct":0},{"id":"D","content":"5","is_correct":0}]},{"id":2484,"subject":"数学","grade":"九年级","stage":"初中","type":"选择题","content":"某学生在学习投影与视图时，观察一个由两个相同圆柱体垂直叠放组成的几何体（下方圆柱体竖直放置，上方圆柱体水平放置在下方圆柱体顶面中央）。若从正前方观察该几何体，所得到的视图最可能是什么形状？","answer":"C","explanation":"该几何体由两个相同圆柱体组成：下方为竖直圆柱，上方为水平圆柱，且水平圆柱位于竖直圆柱顶面中央。从正前方观察时，竖直圆柱的投影是一个长方形（代表其侧面轮廓），而水平圆柱由于与视线方向垂直，其两端呈圆形，但正前方只能看到其侧面投影为一条水平线段，位于长方形的上部中央位置。因此，主视图表现为一个长方形内部包含一条水平线段，对应选项C。选项A忽略了上方圆柱的投影；选项B错误地将水平圆柱投影为完整圆形；选项D引入了不存在的正方形，均不符合实际投影规律。","solution_steps":"","common_mistakes":"","learning_suggestions":"","difficulty":"简单","points":1,"is_active":1,"created_at":"2026-01-10 15:10:48","updated_at":"2026-01-10 15:10:48","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":"一个长方形","is_correct":0},{"id":"B","content":"一个长方形上方叠加一个圆形","is_correct":0},{"id":"C","content":"一个长方形内部包含一条水平线段","is_correct":1},{"id":"D","content":"一个长方形与一个正方形上下排列","is_correct":0}]},{"id":2018,"subject":"数学","grade":"八年级","stage":"初中","type":"选择题","content":"在一次校园绿化项目中，工人在一块矩形空地的四周铺设了宽度相同的步行道。已知原空地的长为 8 米，宽为 6 米，铺设步行道后整个区域（包括步行道）的面积为 120 平方米。若设步行道的宽度为 x 米，则可列方程为：","answer":"B","explanation":"步行道围绕矩形空地四周铺设，宽度为 x 米，因此整个区域的长和宽都要在原来的基础上各增加 2x 米（左右各 x 米，上下各 x 米）。原空地长 8 米，宽 6 米，所以铺设后整个区域的长为 (8 + 2x) 米，宽为 (6 + 2x) 米。根据题意，整个区域的面积为 120 平方米，因此可列方程为：(8 + 2x)(6 + 2x) = 120。选项 B 正确。","solution_steps":"","common_mistakes":"","learning_suggestions":"","difficulty":"简单","points":1,"is_active":1,"created_at":"2026-01-09 10:31:20","updated_at":"2026-01-09 10:31:20","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":"(8 + x)(6 + x) = 120","is_correct":0},{"id":"B","content":"(8 + 2x)(6 + 2x) = 120","is_correct":1},{"id":"C","content":"8x + 6x = 120","is_correct":0},{"id":"D","content":"(8 - 2x)(6 - 2x) = 120","is_correct":0}]},{"id":692,"subject":"数学","grade":"初一","stage":"小学","type":"填空题","content":"在一次班级图书角整理活动中，某学生统计了同学们捐赠的图书类型，其中故事书有15本，科普书比故事书少6本，漫画书是科普书的2倍。那么漫画书有___本。","answer":"18","explanation":"首先根据题意，故事书有15本，科普书比故事书少6本，因此科普书数量为15 - 6 = 9本。漫画书是科普书的2倍，即9 × 2 = 18本。因此漫画书有18本。本题考查的是有理数的基本运算在实际问题中的应用，属于数据的收集、整理与描述知识点范畴，计算过程简单明了，适合七年级学生。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 22:37:16","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":977,"subject":"数学","grade":"初一","stage":"小学","type":"填空题","content":"某学生在整理班级同学的课外阅读时间时，将数据分为5组，每组组距为10分钟，其中一组的数据范围是30分钟到40分钟（不包括40分钟）。若该组中有一个数据为35.5分钟，则这个数据属于第____组。","answer":"4","explanation":"题目中说明数据被分为5组，每组组距为10分钟，且给出的数据范围是30分钟到40分钟（不包括40分钟），即[30, 40)。按照从小到大的顺序分组，第一组为[0,10)，第二组为[10,20)，第三组为[20,30)，第四组为[30,40)，第五组为[40,50)。35.5分钟落在[30,40)区间内，因此属于第4组。本题考查的是数据的收集、整理与描述中的分组知识，属于简单难度，符合七年级数学课程内容。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-30 04:18:27","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":1079,"subject":"数学","grade":"七年级","stage":"初中","type":"填空题","content":"在一次班级环保活动中，某学生收集了可回收垃圾的重量为3.5千克，不可回收垃圾的重量比可回收垃圾少1.2千克。那么，该学生收集的不可回收垃圾的重量是____千克。","answer":"2.3","explanation":"已知可回收垃圾重量为3.5千克，不可回收垃圾比可回收垃圾少1.2千克，因此不可回收垃圾重量为3.5减去1.2，即3.5 - 1.2 = 2.3（千克）。本题考查有理数的减法运算，属于简单难度的实际应用题。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2026-01-06 08:53:52","updated_at":"2026-01-06 08:53:52","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":494,"subject":"数学","grade":"初一","stage":"小学","type":"选择题","content":"某班级进行了一次数学测验，成绩分布如下表所示。根据表格信息，成绩在80分及以上的人数占总人数的百分比最接近以下哪个选项？\n\n| 分数段（分） | 人数 |\n|--------------|------|\n| 60以下 | 5 |\n| 60—69 | 8 |\n| 70—79 | 12 |\n| 80—89 | 15 |\n| 90—100 | 10 |","answer":"C","explanation":"首先计算总人数：5 + 8 + 12 + 15 + 10 = 50（人）。\n成绩在80分及以上的人数包括80—89和90—100两个分数段，共15 + 10 = 25（人）。\n所求百分比为：25 ÷ 50 × 100% = 50%。\n因此，正确答案是C选项。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 18:06:22","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":"40%","is_correct":0},{"id":"C","content":"50%","is_correct":1},{"id":"D","content":"60%","is_correct":0}]},{"id":536,"subject":"数学","grade":"初一","stage":"初中","type":"选择题","content":"在一次环保知识问卷调查中，某班级共收到有效问卷45份。统计结果显示，其中选择‘经常进行垃圾分类’的学生有27人，选择‘偶尔进行垃圾分类’的有12人，其余学生选择‘从不进行垃圾分类’。请问选择‘从不进行垃圾分类’的学生人数占全班有效问卷的百分比是多少？","answer":"B","explanation":"首先计算选择‘从不进行垃圾分类’的学生人数：总人数45减去‘经常’的27人和‘偶尔’的12人，即45 - 27 - 12 = 6人。然后用6除以总人数45，得到比例为6 ÷ 45 ≈ 0.1333，换算成百分比约为13.3%。因此正确答案是B。","solution_steps":null,"common_mistakes":null,"learning_suggestions":null,"difficulty":"简单","points":1,"is_active":1,"created_at":"2025-12-29 18:48:21","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":"10%","is_correct":0},{"id":"B","content":"13.3%","is_correct":1},{"id":"C","content":"15%","is_correct":0},{"id":"D","content":"20%","is_correct":0}]},{"id":1929,"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)、点B(5, y)、点C(x, 7)共线，且线段AC的中点在直线y = 2x - 1上，则x + y的值为____。","answer":"11","explanation":"利用三点共线斜率相等得(y-3)\/3 = (7-y)\/(x-5)，中点((2+x)\/2, 5)代入直线方程得5 = 2·((2+x)\/2) -1，解得x=6，代入得y=5，故x+y=11。","solution_steps":"","common_mistakes":"","learning_suggestions":"","difficulty":"困难","points":1,"is_active":1,"created_at":"2026-01-07 14:10:00","updated_at":"2026-01-07 14:10:00","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":[]}]