某城市地铁线路规划中,需要在平面直角坐标系中确定两个站点A和B的位置。已知站点A位于点(-3, 4),站点B位于第一象限,且满足以下条件:(1) 线段AB的长度为10个单位;(2) 点B到x轴的距离是点B到y轴距离的2倍;(3) 若从站点A出发沿直线行驶到站点B,行驶方向与正东方向形成的夹角为θ,且tanθ = 3/4。现计划在A、B之间增设一个临时站点C,使得AC : CB = 2 : 3。求临时站点C的坐标。
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点A表示的数是-3,点B与点A相距5个单位长度。由于在数轴上向右移动表示数值增大,且点B在原点右侧,说明点B的数值大于0。从-3向右移动5个单位:-3 + 5 = 2,因此点B表示的数是2。选项B正确。
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[{"id":440,"content":"某学生在整理班级同学的课外阅读时间数据时,发现一周内每天阅读时间(单位:分钟)分别为:20,25,30,35,40,45,50。如果将这组数据按从小到大的顺序排列后,位于正中间的那个数称为中位数。那么这组数据的中位数是多少?","type":"选择题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"B","explanation":"题目给出了一组7个数据:20,25,30,35,40,45,50。由于数据个数是奇数(7个),中位数就是排序后位于正中间的那个数,即第(7+1)\/2 = 4个数。将数据从小到大排列后,第4个数是35。因此,这组数据的中位数是35。","options":[{"id":"A","content":"30"},{"id":"B","content":"35"},{"id":"C","content":"40"},{"id":"D","content":"45"}]},{"id":512,"content":"某学生在整理班级同学的身高数据时,制作了如下频数分布表:\n\n身高区间(cm) | 频数\n--------------|------\n140~145 | 3\n145~150 | 5\n150~155 | 8\n155~160 | 10\n160~165 | 4\n\n若该班共有30名学生,则身高在150cm及以上的学生人数占全班人数的百分比是多少?","type":"选择题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"C","explanation":"首先确定身高在150cm及以上的学生人数。根据表格,150~155cm有8人,155~160cm有10人,160~165cm有4人。将这些频数相加:8 + 10 + 4 = 22人。全班共有30名学生,因此所占百分比为 (22 ÷ 30) × 100% ≈ 73.3%。故正确答案为C。","options":[{"id":"A","content":"60%"},{"id":"B","content":"66.7%"},{"id":"C","content":"73.3%"},{"id":"D","content":"80%"}]},{"id":658,"content":"在一次环保主题活动中,某学生收集了不同种类的可回收物品,其中废纸的重量为3.5千克,塑料瓶的重量比废纸多1.2千克,金属罐的重量是塑料瓶的一半。那么金属罐的重量是______千克。","type":"填空题","subject":"数学","grade":"初一","stage":"小学","difficulty":"简单","answer":"2.35","explanation":"首先根据题意,塑料瓶的重量比废纸多1.2千克,废纸为3.5千克,因此塑料瓶重量为3.5 + 1.2 = 4.7千克。金属罐的重量是塑料瓶的一半,即4.7 ÷ 2 = 2.35千克。本题考查有理数的加减与乘除运算在实际问题中的应用,属于简单难度的综合计算题。","options":[]},{"id":1906,"content":"某班级组织了一次环保知识竞赛,参赛学生需完成一份包含10道选择题的试卷。每答对一题得5分,答错或不答扣2分。一名学生最终得分为29分,请问这名学生答对了多少道题?","type":"选择题","subject":"数学","grade":"七年级","stage":"初中","difficulty":"简单","answer":"B","explanation":"设这名学生答对了x道题,则答错或不答的题目数为(10 - x)道。根据得分规则:每答对一题得5分,答错或不答扣2分,总得分为29分,可列出一元一次方程:5x - 2(10 - x) = 29。展开并化简:5x - 20 + 2x = 29 → 7x = 49 → x = 7。因此,这名学生答对了7道题。验证:7×5 = 35分,答错3题扣3×2 = 6分,35 - 6 = 29分,符合题意。","options":[{"id":"A","content":"6道"},{"id":"B","content":"7道"},{"id":"C","content":"8道"},{"id":"D","content":"9道"}]},{"id":2365,"content":"某校八年级开展‘生活中的轴对称’数学实践活动,要求学生从校园建筑、校徽、标志牌等实物中寻找轴对称图形,并测量其关键数据。一名学生记录了三个轴对称图形的对称轴长度(单位:厘米)分别为:√12,2√3,和√27。若将这三个数据按从小到大的顺序排列,正确的是:","type":"选择题","subject":"数学","grade":"八年级","stage":"初中","difficulty":"中等","answer":"B","explanation":"本题考查二次根式的化简与大小比较。首先将每个根式化为最简形式:√12 = √(4×3) = 2√3;√27 = √(9×3) = 3√3;而2√3保持不变。因此三个数分别为:2√3、2√3、3√3。显然,2√3 = 2√3 < 3√3,即前两个相等且小于第三个。所以从小到大的顺序为:2√3 < √12(即2√3)< √27(即3√3)。注意虽然√12化简后等于2√3,但在原始表达式中仍视为独立项,排序时按数值大小处理。故正确选项为B。","options":[{"id":"A","content":"√12 < 2√3 < √27"},{"id":"B","content":"2√3 < √12 < √27"},{"id":"C","content":"√27 < √12 < 2√3"},{"id":"D","content":"√12 < √27 < 2√3"}]},{"id":2238,"content":"某学生在数轴上从原点出发,先向右移动5个单位长度,再向左移动8个单位长度,接着向右移动3个单位长度,最后向左移动6个单位长度。该学生最终所在位置的数与其起始位置(原点)的距离是___。","type":"填空题","subject":"数学","grade":"七年级","stage":"初中","difficulty":"困难","answer":"6","explanation":"该学生从原点0出发,按照顺序移动:+5 → -8 → +3 → -6。计算总位移:5 - 8 + 3 - 6 = -6。最终位置是-6,与原点0的距离是|−6| = 6。题目考查正负数在数轴上的实际应用及绝对值的理解,要求学生掌握连续正负数运算和距离的非负性,属于综合应用型难题。","options":[]},{"id":516,"content":"72°","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":2215,"content":"某学生在记录一周内每天的温度变化时,发现某天的气温比前一天上升了5℃,记作+5℃;而另一天的气温比前一天下降了3℃,应记作____℃。","type":"填空题","subject":"数学","grade":"七年级","stage":"初中","difficulty":"简单","answer":"-3","explanation":"根据正数和负数表示相反意义的量的规则,气温上升用正数表示,下降则用负数表示。因此,气温下降3℃应记作-3℃。此题考查学生对正负数在实际情境中应用的理解,符合七年级正负数表示相反意义的量的知识点。","options":[]},{"id":2013,"content":"如图,在△ABC中,AB = AC,∠BAC = 120°,点D在边BC上,且AD ⊥ BC。若BD = 2,则BC的长度为多少?","type":"选择题","subject":"数学","grade":"八年级","stage":"初中","difficulty":"简单","answer":"A","explanation":"因为AB = AC,△ABC是等腰三角形,且∠BAC = 120°,所以底角∠ABC = ∠ACB = (180° - 120°) ÷ 2 = 30°。由于AD ⊥ BC,且D在BC上,根据等腰三角形性质,AD既是高也是中线,因此BD = DC。已知BD = 2,所以DC = 2,从而BC = BD + DC = 2 + 2 = 4。本题考查等腰三角形性质与轴对称(对称轴为AD),属于简单难度。","options":[{"id":"A","content":"4"},{"id":"B","content":"2√3"},{"id":"C","content":"3"},{"id":"D","content":"2 + √3"}]},{"id":635,"content":"某班级组织学生参加植树活动,男生每人种3棵树,女生每人种2棵树,全班共种了70棵树。已知该班男生人数比女生多5人,那么这个班有多少名女生?","type":"选择题","subject":"数学","grade":"初一","stage":"初中","difficulty":"简单","answer":"B","explanation":"设女生人数为x人,则男生人数为(x + 5)人。根据题意,男生每人种3棵树,女生每人种2棵树,全班共种70棵树,可列方程:3(x + 5) + 2x = 70。展开得:3x + 15 + 2x = 70,合并同类项得:5x + 15 = 70。两边同时减去15:5x = 55。两边同时除以5:x = 11。因此,女生有11人。验证:男生为16人,种树3×16=48棵,女生种树2×11=22棵,总计48+22=70棵,符合题意。","options":[{"id":"A","content":"10"},{"id":"B","content":"11"},{"id":"C","content":"12"},{"id":"D","content":"13"}]}]