发布时间 : 星期四 文章2013-2014学年广东省广州市海珠区七年级(上)期末数学试卷与参考答案更新完毕开始阅读7c731cc5f4335a8102d276a20029bd64783e62ae
超过28立方米但不超过50立方米的部分 超过50立方米的部分 b a+1.5 2013年7月份，该市甲户居民用水9立方米，交水费18元；乙户居民用水36立方米，交水费76元． （1）求上表中a与b的值；
（2）当某户居民月用水量为x立方米时，请用含x的式子表示应付水费； （3）试行“阶梯水价”收费以后，该市某户居民月用水多少立方米时，其当月的平均水价每立方米恰好2.15元？
【解答】解：（1）a=18÷9=2， b=（76﹣28×2）÷（36﹣28） =20÷8 =2.5．
故a的值为2，b的值为2.5；
（2）当0＜x≤28时，用含x的式子表示应付水费为2x；
当28＜x≤50时，用含x的式子表示应付水费为2.5（x﹣28）+2×28=2.5x﹣14； 当x＞50时，用含x的式子表示应付水费为（2+1.5）（x﹣50）+28×2+（50﹣28）×2.5=3.5x﹣64；
（3）设该市某户居民月用水y立方米时，依题意有 2.15y=2.5y﹣14， 解得y=40．
故该市某户居民月用水40立方米时，其当月的平均水价每立方米恰好2.15元．
24．（14分）在数学的学习过程中，我们经常用一下的探索过程解决相关问题数学问题：平面内有1个点，如果在平面内再添加n个点，并过这n+1个点中任意两点画直线，那么最多可以画出多少条直线？ 添加点的个第13页（共15页）
图形 最多可画出的直线条数
数 1 2 1 3 3 ？ …
… … 【解答】解：平面内有1个点，如果在平面内再添加1个点，并过这2个点可以画一条直线；
平面内有1个点，如果在平面内再添加2个点，并过这3个点最多可以画×3×（3﹣1）=3条直线；
平面内有1个点，如果在平面内再添加3个点，并过这4个点最多可以画×4×（4﹣1）=6条直线； …
平面内有1个点，如果在平面内再添加n个点，并过这n+1个点中任意两点画直线，那么最多可以画出n（n+1）条直线．
并列句 and 和，并且， work hard, and you can pass the exam.but 但是 he is rich but he is not happy. Or 否则，要不然，或者（在否定句中表和） Hurry up, or you’ll be late. so 因此，所以 Kate was ill so she didn’t go to school. For 因为 I have to stay up late, for I have a lot of work to do. 状语从句 当状语从句的引导词为If, when, before, after, until, as soon as 等，主句和从句有下列情况： 英语句子中如果一看到 Thought----but----; because----so---这种结构,就是错误.倒装句 so+助动词\\BE动词\\情态动词+另一主语，表示后者与前者一致。so+上句主语+助动词\\BE动词\\情态动词，真的，确实如此。 Tom watched TV last night, so did Ann. Tom didn’t watch TV last night. Neither did Ann. ---You’ve left the light on. ---So I have. I’ll go and turn it off. 宾语从句 赠送—初中英语总复习知识点归纳 第14页（共15页）
?从句用陈述句语序。?主句与从句的关系。 A．主现从不限；B．主过从过； C．真金不怕火炼。The earth moves around the sun. ③常见的宾语从句。 She says that ---- I hope / think / feel / wonder---- I wonder if he will join us in the discussion tonight. Could you tell / show me--- Could you please tell me where the teacher’s office is? Do you know---- Do you know where Mr. Li lives? Please tell me --- She asked me --- I don’t know ---- I don’t know whether Tom will go or not.定语从句 that和which在指物的情况下一般都可以互换, 但在下列情况下, 一般用that而不用which。 (1) 先行词为all, everything, nothing, something, anything, little, much 等不定代词时。 I am sure she has something (that) you can borrow. (2)先行词被all, every, no, some, any, little, much等修饰时。I’ve read all the books that are not mine. (3)先行词被序数词或最高级修饰时。This is the first book (that) he has read. (4)先行词被the only, the very, the same, the last修饰时。 This is the very book that belongs to him.一般用that而不用who (1) 先行词是who或who引导的主句。 Who is the girl (that) drove the car? Who (that) broke the window will be punished. (2) 主句以There be 引导时 。 There are 200 people (that) didn’t that和which在指物的情况下一般都可以互换, 但在下列情况下, 一般用which而不用that。 (1)关系代词在限制性定语从句中紧跟介词作宾语（介词提前）。 Those are many trees under (which) they can have a rest. (2) 在非限制性定语从句中。 Football , (which) is a very popular game, is played all over the world. 后跟ing 的词有Finish doing Before 2008 Beijing we will finish building the Olympic Park. enjoy doing 喜欢做某事 I enjoy reading English loudly. mind doing 介意（反对）做某事 would you mind opening the window? practice doing sth. 练习做某事 we should practice speaking English as often as possible. be busy doing sth. 忙于做某事 be worth doing sth. 值得做某事 feel like doing sth =want to do sth. 想要做某事spend --- (in) doing sth 花费时间做某事 stop / prevent / keep ----from doing 阻止某人做某事have trouble \\problem / a hard time doing sth. 做某事很困难 Have fun doing sth. =have a good time doing sth. 做某事很快乐go on doing sth 接着做原来做着的事 go shopping / swimming/ skating /surfing---do some running / washing/ cooking --- 介词(for, with, without, about ---) 后跟动词原形:why don't you why not you'd better (not) would you please (not) make\\ let \\ have\\ [注意: 在被动语态中, t o 要加上]
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