2023九师联盟压轴题及答案

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范文：Dear Jim,How's everything?I'm writing to invite you to give us an online talk on English writing.Our classmates seem to be weak inorganisation.Would you please give us some suggestions on how to connect sentences logically,how to develop aparagraph,and how to structure an essay?The talk will be about an hour,and you can decide on a date at your convenience.Please let me know whichplatform you'll be using.It would be great if we could have a 10-minute question and answer session at the end ofplatform you'll be using.It would be great if we could have a 10-minute question and answer session at the end ofyour talk.Looking forward to your reply.Yours,Li Hua

20.【解析】频率组距0.0350.0300.0250.0200.0150.0100.005005060708090100分数(I)由题意有1-(0.010+2×0.015+0.025+0.005)×10=0.3，频率0.3=0.030,如图.…(（2分)组距10(Ⅱ)平均分为：0.1×45+0.15×55+0.15x65中0.3×75+0.25×85+0.05×95=71，·(4分)前三组的频率之和为0.4，第四组频率为0.3，所以中位数在第四组，(Ⅱ）平习分为：0.1×45+0.15×5540.15×65中0.3×75+0.25×85+0.05×95=71，…(4分)前三组的频率之和为0.4，第四组频率为0.3，所以中位数在第四组，中位数为：70+10x0.5÷04220(6分)0.33第三组频率最大，所以众数为：70+80=75.(7分)2(Ⅲ)成绩在[60,70)有60×0.15=9人，成绩在[70,80)有60×0.3=18人，现按照比例分配的分层随机抽样方法抽取6人，则成绩在[60,70)抽取的人数为。6。×9=2入，9+18成绩在[70,80)抽取的人数为、6x18=4人，…(9分)9+18从这6人中选2人有C。=15种选法，选出的这2名学生来自同一分数段有C?+C?=7种.…（11分）7所以，选出的这2名学生来自同一分数段的概率为P=…(12分)15