在数轴上,点A表示的数是-4,点B表示的数是6。某学生在数轴上标出了点C,使得点C到点A的距离是点C到点B的距离的2倍。那么点C表示的数可能是多少?
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设全班共有x人。根据题意,喜欢跳绳的人数为30%x = 0.3x,喜欢踢毽子的人数为0.3x + 10,喜欢打羽毛球的人数为28。总人数为三部分之和:0.3x + (0.3x + 10) + 28 = x。解这个方程:0.6x + 38 = x,移项得38 = 0.4x,解得x = 95 ÷ 0.4 = 60。因此全班有60人。喜欢踢毽子的人数为0.3 × 60 + 10 = 18 + 10 = 28人。题目考查了百分数的应用和一元一次方程的建立与求解,属于数据的收集、整理与描述和一元一次方程的综合应用。
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[{"id":2479,"content":"如图,一个圆锥的底面半径为3 cm,母线长为5 cm,则该圆锥的侧面展开图(扇形)的圆心角是多少度?","type":"选择题","subject":"数学","grade":"九年级","stage":"初中","difficulty":"简单","answer":"A","explanation":"圆锥的侧面展开图是一个扇形,其弧长等于圆锥底面的周长,半径等于圆锥的母线长。\n\n1. 计算底面周长:C = 2πr = 2π × 3 = 6π(cm)。\n2. 扇形半径为母线长5 cm,设圆心角为θ度,则扇形弧长公式为:(θ\/360) × 2π × 5 = (θ\/360) × 10π。\n3. 令扇形弧长等于底面周长:(θ\/360) × 10π = 6π。\n4. 两边同时除以π,得:(θ\/360) × 10 = 6。\n5. 解得:θ = (6 × 360) \/ 10 = 216°。\n\n因此,该圆锥侧面展开图的圆心角为216°,正确答案为A。","options":[{"id":"A","content":"216°"},{"id":"B","content":"180°"},{"id":"C","content":"150°"},{"id":"D","content":"120°"}]},{"id":1917,"content":"某班级进行了一次数学测验,成绩分布如下表所示。若将成绩分为“优秀”(90分及以上)、“良好”(75~89分)、“及格”(60~74分)和“不及格”(60分以下)四个等级,则成绩为“良好”的学生人数占总人数的百分比是多少?\n\n| 分数段 | 人数 |\n|--------------|------|\n| 90~100 | 8 |\n| 75~89 | 12 |\n| 60~74 | 6 |\n| 60以下 | 4 |","type":"选择题","subject":"数学","grade":"七年级","stage":"初中","difficulty":"简单","answer":"B","explanation":"首先计算总人数:8 + 12 + 6 + 4 = 30(人)。成绩为“良好”(75~89分)的学生有12人。因此,“良好”等级所占百分比为:(12 ÷ 30) × 100% = 40%。故正确答案为B。","options":[{"id":"A","content":"30%"},{"id":"B","content":"40%"},{"id":"C","content":"50%"},{"id":"D","content":"60%"}]},{"id":245,"content":"某学生计算一个数的相反数时,将该数加上3,结果得到8,那么这个数的相反数是____。","type":"填空题","subject":"数学","grade":"初一","stage":"小学","difficulty":"简单","answer":"-5","explanation":"设这个数为x。根据题意,某学生将这个数加上3得到8,即x + 3 = 8,解得x = 5。那么这个数的相反数是-5。题目考查的是相反数的概念和一元一次方程的简单应用,符合七年级数学课程内容。","options":[]},{"id":476,"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记录如下:纸类3.5千克,塑料比纸类少1.2千克,金属是塑料重量的2倍。请问该学生收集的金属垃圾重量是多少千克?","type":"选择题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"A","explanation":"首先根据题意,纸类重量为3.5千克。塑料比纸类少1.2千克,因此塑料重量为:3.5 - 1.2 = 2.3(千克)。金属是塑料重量的2倍,所以金属重量为:2.3 × 2 = 4.6(千克)。因此正确答案是A。本题考查有理数的加减与乘法运算在实际问题中的应用,符合七年级有理数章节的学习要求。","options":[{"id":"A","content":"4.6"},{"id":"B","content":"5.8"},{"id":"C","content":"6.4"},{"id":"D","content":"7.0"}]},{"id":567,"content":"平均数是5.2,中位数是5,众数是5","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":621,"content":"在一次校园环保活动中,某班级收集了可回收垃圾的重量记录如下:纸类占总重量的40%,塑料类比纸类少10千克,金属类是塑料类的一半,其余为玻璃类,重6千克。若设总重量为x千克,则根据题意列出的正确方程是","type":"选择题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"A","explanation":"根据题意,纸类占总重量的40%,即0.4x千克;塑料类比纸类少10千克,即(0.4x - 10)千克;金属类是塑料类的一半,即0.5 × (0.4x - 10)千克;玻璃类已知为6千克。四类垃圾重量之和应等于总重量x千克,因此方程为:0.4x + (0.4x - 10) + 0.5(0.4x - 10) + 6 = x。选项A正确表达了这一关系。其他选项中,B错误地将塑料类表示为比纸类多10千克,C将金属类误写为塑料类的2倍,D对塑料类的表达方式错误,不符合题意。","options":[{"id":"A","content":"0.4x + (0.4x - 10) + 0.5(0.4x - 10) + 6 = x"},{"id":"B","content":"0.4x + (0.4x + 10) + 0.5(0.4x + 10) + 6 = x"},{"id":"C","content":"0.4x + (0.4x - 10) + 2(0.4x - 10) + 6 = x"},{"id":"D","content":"0.4x + (x - 0.4x - 10) + 0.5(x - 0.4x - 10) + 6 = x"}]},{"id":787,"content":"在一次班级数学测验成绩整理中,某学生将10名同学的成绩按从小到大的顺序排列,得到的数据为:72,75,78,80,82,85,88,90,93,96。这组数据的中位数是____。","type":"填空题","subject":"数学","grade":"初一","stage":"小学","difficulty":"简单","answer":"83.5","explanation":"中位数是指将一组数据按大小顺序排列后,处于中间位置的数。当数据个数为偶数时,中位数是中间两个数的平均值。本题中有10个数据(偶数个),因此中位数是第5个和第6个数据的平均数。第5个数是82,第6个数是85,所以中位数为 (82 + 85) ÷ 2 = 167 ÷ 2 = 83.5。","options":[]},{"id":831,"content":"某学生测量了一个长方体的长、宽、高分别为 3 厘米、4 厘米和 5 厘米,则该长方体的体积是 _ 立方厘米。","type":"填空题","subject":"数学","grade":"初一","stage":"小学","difficulty":"简单","answer":"60","explanation":"长方体的体积计算公式为:体积 = 长 × 宽 × 高。将已知数据代入公式:3 × 4 × 5 = 60。因此,该长方体的体积是 60 立方厘米。本题考查几何图形初步中的立体图形体积计算,属于七年级数学基础知识点。","options":[]},{"id":15,"content":"Fill in the blank: I have _____ (go) to school every day.","type":"填空题","subject":"英语","grade":"初二","stage":"初中","difficulty":"中等","answer":"to go","explanation":""have to"表示"必须,不得不",后接动词原形。","options":[]},{"id":200,"content":"一个长方形的长是8厘米,宽是5厘米,它的周长是______厘米。","type":"填空题","subject":"数学","grade":"初一","stage":"小学","difficulty":"简单","answer":"26","explanation":"长方形的周长计算公式是:周长 = 2 × (长 + 宽)。将已知的长8厘米和宽5厘米代入公式,得到:2 × (8 + 5) = 2 × 13 = 26(厘米)。因此,这个长方形的周长是26厘米。","options":[]}]