2019－2022高二英语周报第二十期答案

书面表达One possible version:NOTICEA sports meeting will be held in the playground of our school from next Thursday to FridayAs you know, the pressure of study is very heavy now, especially for those senior 3. So the purpose of the sports meeting is to letevery student get relaxed, as a result of which we students can live happily and heal thilyEveryone is welcome to take part in it. Those who perform excellently at the sports meeting will get prizes. But don' t take theresults so serously because taking part is more important than the result. Good luck to everyone!

20.【答案】(1)解:由题意知:1200×20-1000=23000,1200×15-1000=17000,900×20-1000=17000,900×15-1000=12500所以X的所有可能取值为:23000,17000,1250分设A表示事件“作物产量为900kg,则P=0.5B表示事件作物市场价格为15元/kgP(B)=0.4P(x=23000=PA·B)=(1-051-04)=0,3P(x=17000)=PAB)+PA·B)=(1-0,5)×04+05×(1-04)=05P(x=12500)=P(A·B)=05×04=0。2所以X的分布列为1700025000.30.50.2分解:由(1)知,2020年该衣户种植该经济农作物一亩的预计纯收入为E(x)=23000×0,3+17000×0.5+12500×0.2=17900(元179004>4000凭这一亩经济农作物的纯收入,该农户的人均纯收入超过了国家脱贫标准所以,能预测该农户在2020年底可以脱贫12分

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