某公园计划修建一个等腰三角形花坛,其底边长为8米,两腰相等。为了加固结构,工人从顶点向底边作一条垂直线段,将花坛分成两个全等的直角三角形。若这条垂直线段的长度为3米,则该等腰三角形的周长是多少米?
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首先根据题意,原来有5个小组,每组12千克,所以总纸张重量为 5 × 12 = 60 千克。后来增加了3个小组,总小组数变为 5 + 3 = 8 个。将60千克纸张平均分给8个小组,每个小组分到 60 ÷ 8 = 7.5 千克。本题考查了一元一次方程的实际应用和整数的除法运算,属于简单难度,符合七年级学生对有理数和一元一次方程知识点的掌握水平。
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[{"id":204,"content":"某学生在计算一个数减去3.5时,误将减号看成了加号,结果得到8.2。正确的计算结果应该是____。","type":"填空题","subject":"数学","grade":"初一","stage":"小学","difficulty":"简单","answer":"1.2","explanation":"该学生误将减法做成了加法,即把原数加上3.5得到了8.2。因此可以先求出原数:8.2 - 3.5 = 4.7。然后用正确的运算方式计算:4.7 - 3.5 = 1.2。所以正确答案是1.2。","options":[]},{"id":1,"content":"若x=3是方程2x + a = 7的解,则a的值为?","type":"选择题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"A","explanation":"将x=3代入方程2x + a = 7,得2*3 + a = 7,解得a = 1。","options":[{"id":"A","content":"1"},{"id":"B","content":"-1"},{"id":"C","content":"2"},{"id":"D","content":"3"}]},{"id":479,"content":"某班级组织了一次环保活动,收集废旧纸张进行回收。活动结束后,统计了5个小组的回收量(单位:千克),分别为:8.5、7.2、9.0、6.8、8.5。请问这5个小组回收量的中位数是多少?","type":"选择题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"B","explanation":"要找出中位数,首先需要将数据按从小到大的顺序排列:6.8、7.2、8.5、8.5、9.0。由于共有5个数据(奇数个),中位数就是正中间的那个数,即第3个数。排序后第3个数是8.5,因此中位数是8.5。选项B正确。","options":[{"id":"A","content":"7.2"},{"id":"B","content":"8.5"},{"id":"C","content":"8.0"},{"id":"D","content":"9.0"}]},{"id":584,"content":"某学生在整理班级同学的课外阅读时间时,随机抽取了30名学生进行调查,发现每天阅读时间在0.5小时到1.5小时之间。他将这些数据分为5组,并制作了频数分布表。若每组组距相同,则每组的组距是多少小时?","type":"选择题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"B","explanation":"题目中给出的数据范围是从0.5小时到1.5小时,因此全距为1.5 - 0.5 = 1.0小时。将数据分为5组,且每组组距相同,则组距 = 全距 ÷ 组数 = 1.0 ÷ 5 = 0.2小时。因此正确答案是B选项。","options":[{"id":"A","content":"0.1"},{"id":"B","content":"0.2"},{"id":"C","content":"0.3"},{"id":"D","content":"0.4"}]},{"id":672,"content":"在一次班级大扫除中,某学生负责统计擦窗户和拖地的人数。已知擦窗户的人数比拖地人数的2倍少3人,而两项工作总共有27人参与。设拖地的人数为x,则根据题意可列出一元一次方程:___。","type":"填空题","subject":"数学","grade":"初一","stage":"小学","difficulty":"简单","answer":"x + (2x - 3) = 27","explanation":"设拖地的人数为x,则擦窗户的人数为2x - 3(因为比拖地人数的2倍少3人)。两项工作总人数为27人,因此拖地人数加上擦窗户人数等于27,即x + (2x - 3) = 27。该方程正确反映了题目中的数量关系,属于一元一次方程的实际应用,符合七年级数学课程要求。","options":[]},{"id":2145,"content":"某学生在解方程时,将方程 2x + 3 = 7 的解写为 x = 2。以下哪个步骤正确地验证了这个解?","type":"选择题","subject":"数学","grade":"七年级","stage":"初中","difficulty":"简单","answer":"A","explanation":"验证方程解的正确方法是将解代入原方程,检查等式是否成立。将 x = 2 代入 2x + 3 = 7,得 2×2 + 3 = 4 + 3 = 7,等式成立,说明 x = 2 是正确解。选项 A 正确展示了这一过程。其他选项计算错误或代入方式不正确。","options":[{"id":"A","content":"将 x = 2 代入原方程,得到 2×2 + 3 = 7,计算得 4 + 3 = 7,等式成立,因此解正确。"},{"id":"B","content":"将 x = 2 代入原方程,得到 2×2 + 3 = 7,计算得 4 + 3 = 8,等式不成立,因此解错误。"},{"id":"C","content":"将 x = 2 代入原方程,得到 2 + 2 + 3 = 7,计算得 7 = 7,因此解正确。"},{"id":"D","content":"将 x = 2 代入原方程,得到 2×2 = 4,4 + 3 = 6,因此解错误。"}]},{"id":2313,"content":"在一次校园绿化项目中,工人师傅需要在一块矩形空地的对角线上铺设一条石板路。已知这块空地的长为8米,宽为6米。为了估算石板数量,需要先计算对角线的长度。根据勾股定理,这条对角线的长度最接近以下哪个值?","type":"选择题","subject":"数学","grade":"八年级","stage":"初中","difficulty":"简单","answer":"B","explanation":"本题考查勾股定理在矩形对角线计算中的应用。矩形对角线将矩形分成两个直角三角形,其中两条直角边分别为矩形的长和宽。根据勾股定理:对角线² = 长² + 宽² = 8² + 6² = 64 + 36 = 100。因此,对角线 = √100 = 10(米)。故正确答案为B。","options":[{"id":"A","content":"9米"},{"id":"B","content":"10米"},{"id":"C","content":"11米"},{"id":"D","content":"12米"}]},{"id":798,"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。共收集了12件工具,其中扫帚和拖把的总数是抹布数量的2倍,而抹布比扫帚多1件。设扫帚有x件,拖把有y件,抹布有z件,则可列出二元一次方程组:x + y + z = 12,x + y = 2z,z = x + 1。由这三个方程可得,扫帚有___件。","type":"填空题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"3","explanation":"根据题意,已知三个方程:(1) x + y + z = 12(总工具数),(2) x + y = 2z(扫帚和拖把是抹布的2倍),(3) z = x + 1(抹布比扫帚多1件)。将(3)代入(2)得:x + y = 2(x + 1),化简得 x + y = 2x + 2,即 y = x + 2。再将z = x + 1和y = x + 2代入(1):x + (x + 2) + (x + 1) = 12,合并同类项得 3x + 3 = 12,解得 3x = 9,x = 3。因此,扫帚有3件。","options":[]},{"id":568,"content":"总人数40人,百分比55%","type":"选择题","subject":"数学","grade":"初一","stage":"小学","difficulty":"简单","answer":"待完善","explanation":"解析待完善","options":[]},{"id":1080,"content":"在一次环保活动中,某学生收集了可回收垃圾和不可回收垃圾共12千克,其中可回收垃圾比不可回收垃圾多4千克。设不可回收垃圾为x千克,则可列出一元一次方程为:______。","type":"填空题","subject":"数学","grade":"七年级","stage":"初中","difficulty":"简单","answer":"x + (x + 4) = 12","explanation":"设不可回收垃圾为x千克,根据题意,可回收垃圾比不可回收垃圾多4千克,因此可回收垃圾为(x + 4)千克。两者总重量为12千克,所以方程为x + (x + 4) = 12。该题考查一元一次方程的实际建模能力,属于简单难度。","options":[]}]