1、学而思教案篇一：奥数和差问题教案五年级奥数第二讲 和差问题知识点拨：和差问题是已知大小两个数的和与这两个数的差，求大小两个数各是多少的应用题为了解答这种应用题，首先要弄清两个数相差多少的不同叙述方式.有些题目明确给了两个数的差，而有些应用题把两个数的差“暗藏”起来，我们管暗藏的差叫“暗差” 。知道两个数的和，以及它们的差，要求这两个数，解决和差问题需要我们画线段图来分析，方法如下：方法一： (和+ 差) 2=大数 和- 大数=小数方法二： (和- 差) 2=小数 和- 小数= 大数例题精讲【例 1】长方形操场的长与宽相差 80 米，沿操场跑一周是400 米，求这个操场的长与宽是多少米？【解析】
2、长方形一周的长是指两条长和两条宽的和，由条件可知一条长与一条宽的和为 (米) ，由此我们就知道了长和宽之和是 200 米，又知道长和宽之差是 80 米，根据和差问题来解答： 方法一：长： (米) 宽：（米）方法二：宽： (米)长：（米）练一练丁丁在期中考试时，语文、数学两科平均分是 91 分，数学比语文多 2 分，那么丁丁语文和数学各得了多少分？【例 2】小勇家养的白兔和黑兔一共有 22 只，如果再买 4 只白兔，白兔和黑兔的只数一样多小勇家养的白兔和黑兔各多少只？【解析】解决这道题的关键就是理解“如果再买 4 只白兔，白兔和黑兔的只数一样多” ，这句话的意思也就是白兔的只数比黑兔的只数少 4
3、 只，或黑兔的只数比白兔多 4 只只要理解了这个已知条件，我们就可以把这个题转换成典型和差问题来解决了方法一：把黑兔多的 4 只减掉，看成两个白兔的数量来计算列式：白兔：（只） ，黑兔： (只) 或 (只)方法二：把白兔少的 4 只加上，看成两个黑兔的数量来计算列式：黑兔： (只) ，白兔： (只) 或 (只)练一练图书馆的书架上、下两层共存书 220 本，如果从上层拿出 10本放入下层，则两层书架上书数相等求原来上、下层各存书多少本？【 例 3】有三块布料一共 190 米，第二块比第一块长 20 米，第三块比第二块长 30 米每块布料各长多少米？【解析】先画线段图，从线段图可以看出，以第一块
4、为标准，第二块减少 20 米，第三块减少 (米 )，总和减少 (米)，即( 米)120 米相当于第一块布料长的 3 倍，求出第一块布料的长度，第二块、第三块就可以求出 第一块布料长度的 3 倍是： (米) 第一块布料的长度是： (米) 第二块布料的长度是： (米) 第三块布料的长度是： (米)练一练有 3 条绳子，共长 95 米，第一条比第二条长 7 米，第二条比第三条长 8 米，问 3 条绳子各长多少米？【例 4】甲、乙两校共有学生 1050 人，部分学生因搬家需要转学，已知由甲校转入乙校 20 人，这样甲校比乙校还多 10 人，求两校原来有学生多少人？【解析】这道题虽然只告诉了我们两个数的
5、和，但是两数的差属于隐藏条件由甲校转入乙校 20 人，这样甲校比乙校还多10 人，实际上甲校比乙校多 (人) ，找到了隐藏的差，就转变成了典型的和差问题列式：乙： (人) 甲： (人)练一练小华和小敏共有铅笔 25 枝，如果小华用去 4 枝，小敏用去 3枝，那么小华还比小敏多 2 枝，小华和小敏原来各有多少枝铅笔？【例 5】周明和王刚两人数学成绩的和是 182 分周明如果多考 5 分，就比王刚多 3 分周明和王刚的数学各考了多少分？【 解析】已知周明和王刚两人数学成绩的和是 182 分，根据条件“周明如果多考 5 分，就比王刚多 3 分“可知，王刚的数学成绩比周明多（分） 转换成和差问题解答如
6、下： 方法一：王刚：（分）周明：（分）方法二：周明：（分）王刚：（分）练一练有大、小两个油桶，一共装油 24 千克，两个油桶都倒出同样多的油后分别还剩 9 千克和 5 千克问：原来大、 小两个油桶各装油多少千克？【例 6】兔妈妈拔了 29 个萝卜分给了小白兔和小黑兔，因为分的萝卜不一样多，兔妈妈让小白兔给了小黑兔 5 个，这时再来数发现小黑兔比小白兔多出 1 个萝卜，你知道原来小白兔和小黑兔各分到了多少个萝卜吗？【 解析】这道题关键也是要找到暗差，小白兔给了小黑兔 5 个后，小黑兔又比小白兔多出 1 个萝卜，画图来分析，可以得出原来小白兔比小黑兔多个萝卜这时就可以根据和差问题问题来解决了方法一
7、：小白兔：（个） ，小黑兔：（个）方法二：小黑兔：（个） ，小白兔：（个） 练一练甲乙两个仓库共存大米 56 包，从乙仓库调 8 包到甲仓库，两个仓库大米的包数就同样多了，甲、乙两个仓库原有大米各多少包？【例 7】甲校原来比乙校多人，为方便就近入学，甲校有若干人转入乙校，这时甲校反而比乙校少人甲校有多少人转入乙校？【 解析】利用移多补少思想思考， （人） ，当甲校转入乙校 24人时，那么甲乙两校的人数就一样多，当甲校继续有同学转入到乙校时，每转入一个同学，甲校就比乙校少 2 人， ，当再从甲校转入 6 人到乙校时，甲校就比乙校少 12 人，所以甲校一共转入乙校（人）时，甲校就比乙校少 12 人
8、练一练两箱图书共有 66 本，甲箱如果借出 10 本，就比乙箱少 4本甲、乙两箱原有图书各多少本？课后作业1. 小明期末考试时语文和数学的平均分数是 94 分，数学比语文多 8 分，问语文和数学各得多少分？2. 甲、乙两桶油共重 30 千克，如果把甲桶中 6 千克油倒入乙 桶，那么两桶油重量相等，问甲、乙两桶原有多少油？3. 学而思学校新进 99 本书，分给三、四、五三个年级，三年级比四年级多分了 2 本，四年级比五年级多分了 5 本，三个年级各分得多少本书?4. 草地上有黑兔、白兔、灰兔共 27 只，黑兔比白兔多 2 只，灰兔比白免少 2 只黑兔、白兔、灰兔各有多少只？5. 哥弟俩共有邮票
9、70 张，如果哥哥给弟弟 4 张邮票，这时哥哥还比弟弟多 2 张。哥哥和弟弟原来各有邮票多少张？6. .甲、乙两桶油共重 30 千克，如果把甲桶中 6 千克油倒入乙 桶，那么两桶油重量相等，问甲、乙两桶原有多少油？7. 一只两层书架共放书 72 本，若从上层中拿出 9 本给下层，上层比下层多 4 本。上、下层各放书多少本？8. 方方和圆圆共有图书 70 本，如果方方给圆圆 5 本，那么圆圆就比方方多 4 本问：方方和圆圆原来各有图书多少本？第 3 页 共 7 页篇二：高三全册数学教案篇三：教案Unit 6 Good MannersPeriod 1.Warning up and Listenin
10、gTeaching Aims and Demands: To learn some expression of apologies and response properly toapologies. To listen focusing on key words and important sentences .Warming up: step 1 To invite two pairs to play two short plays.First, Situation 1Because today is As birthday, she wants to invite B to her bi
11、rthdayparty. In the morning, A meets B on the way to the school. A invites B, but Bs father have told B that he must look after Bs younger brother at night. So B cant go to As party. B apologizes for it and wish A happybirthday.Situation Between class, A is running around the classroom. At that time
12、, B drops his pen and A steps on it and breaks it.Step 2Look at the 4 pictures on the page 36.1)What do you think is happening in every picture?2)Can you make a dialogue for every picture?Complete the dialogues with proper words according to the situation given.Step 3Discuss in groups, What are good
13、 manners?After discussion, fill in the next tableGood mannersBad mannersAsk Ss:Do you think you are a person with good manners? Can you tell us a story as an example? .Listening.1)Listen to the tape with this questionHow many times does Bill apologize?2)Listen to the tape for the second time, summar
14、ize two problems3)Listen to the tape for the last time and fill in the blanks. Check the answers and exercise the expressions of apology.4)Workbook: Listening .Homework: Make two dialogues with your partner about apologies.Period 2. Speaking and TalkingTeaching Aims and Demands: To use the expressio
15、ns of apologies and possible answers freely through some situations. To distinguish what good manners are and what bad manners are .Step 1Speaking. Practice different expressions.For example:” Forgive me, Im very sorry!” is quite formal. While “Oops, Sorry about that” is a very informal way.To help
16、students understand that in what situations they should use formal expression and in what situations they should use informalexpressions.In these exercise, Ss have to imagine themselves at a party. Everyone is very polite. They should talk to each other politely and make excuse when troubling others
17、. Then ask Ss to work in groups and consider the following three situations.Sample: Dialogue 1A: Arent you going to introduce me to him?B: Oh, forgive me. I didnt know you hadnt met. Danna, this is Alex. A: Hi, Alex. Nice to meet you!Choose three groups to reports.Step 2Talking1)Read the following s
18、ituations carefully2)Divide the whole class into 6groups. Every two groups make a dialogue. One is Pros and the other is Cons. Every group should list their opinions to try their best to persuade the other group. Discuss in groups.3)According to their opinions, two groups make a dialogue. They shoul
19、d be against the opinions of the other group and give their opinions. .Homework:1)Choose one of the situations in Talking to write a dialogue2)Preview ReadingPeriod 3. Reading ?Teaching Aims and Demands: To get to know the western talk manners To compare Chinese table manners with western table mann
20、ers Improve the reading ability of the Ss, especially the skills of summarizing and scanning.Step 1 Warming up1)Teacher tells a story of a Chinese at a western dinner party who made a fool of himself due to the lack of cultural background.The story is: Once a Chinese was invited to an American dinne
21、r party. When he saw the napkin on the table, he tied it around his neck just as Chinese parents do to their children when theyre fed. As a result, he made a fool of himself.2)Teacher then presents the tools on the table and shows how to put these knives and forks and how to use them. Then ask one s
22、tudent to imitate.3)Brainstorming Judge these manners. Which are good and which are bad. Can you speak with your mouth full? Can you use your hand to take food from the plate? Is it polite to touch the glasses when you toast? Is it polite to persuade others to drink up after toasting?4) Do Pre-readi
23、ng, discuss in groupsSituations Rules for being polite in Chinese cultureAt a dinner paryGreeting your teacherReceiving a birthday presentPaying a visit to a friends houseAsk three Ss to finish this table.Step 2 Reading Ss do scanning for exercise 2( 3minutes for scanning)In what order will the foll
24、owing dishes be served at a western dinnerpartydessert drinkmain course starter sousummarize the main idea of every paragraph (答案见教参P136) With following questions, listen to the tape and read carefully.1). Instead of a hot, damp cloth, napkin is often seen at the Chinesedinner party nowadays. What s
25、ign do you think it implies? How can you use it?2). What do soft drinks refer to? Is white or red wine a soft drink?3). Do people say anything or keep silent when drinking to ones health or drinking a toast? What do you usually do if you drink a toast?Ask some Ss to answer these questions and do exe
26、rcise 3Homework:1). Do practice on P116-1172). Preview languages study and grammarPeriod 4.Reading ?Teaching Aims and Demands: To learn some useful expressions about table manners. To learn some useful words and sentencesStep 1 Carefully Reading1). Explain some words and expressions( apologize, tabl
27、e manne(本文来自：Www.bdfqY.cOm 千 叶帆文 摘:学而思教案)rs,impression) (See the teachers book in P121-122,P127-128)2). Analyze some complex sentences( In China, you sometimes get a hot, damp cloth, to clean your face and hands, which, however, is not thecustom in Western countries). (See the teachers book in P121-
28、122)3). Sum up the textFinish the exercise 2 on P40 custom A long, thing, curly strips of pasta; usually used in Chinese and Italian cooking toast B. a pair of thing sticks which people in China and Far East use to eat their food with breastC. slightly wet dishesD. center. middle E. a practice follo
29、wed by people of a particular group or region dampF. a utensil consisting of a small, shallow bowl on a handle, used in preparing, serving, or eating food chopsticks G. the supper part of your chest; the front part of a birds body tender H. the hard parts inside your body and all the animals which t
30、ogether form the skeleton spirits I. Food that is prepared in a particular style noodles J. easy to cut or chew; sb.or sth that is tender expresses gentle and caring feelings spoon K. the act of raising a glass and drinking in honor of or to the health of a person or thing bones L. strong alcoholic
31、drinks such as whisky and Chinese Maotai Step 2 Post-reading1.Discussion:We are very familiar with table manners in China. But in those years,table manners are slowly changed. Can you point out which manners are also changed? Give some examples.2.Ask some groups to reportStep 3 Finish the exercise 2
32、 on P40 and check the answer (ask one student to show his answer). Check the answers on P116-117Homework:Write a short passage about the discussion.Period 5 Language Study and GrammarTeaching Aims and Demands: To learn word formation and the meaning of prefixes, such as in-, im-, un-, non- To consol
33、idate the Attributive Clauses, both restrictive andnon-restrictive through some exercises.Step 1. Explain the formation of the word and the function of prefixes. Do exercise on P40 to point out which of the following words have negative prefixes.Nonstop unfold incorrect important understandInvite un
34、lucky impossible uniform interesting Matching exerciseUn-smokingNon- possibleDis-ableIm- likeAnswer: unable, non-smoking, dislike, impossible Blank- filling with the above words( using Restrictive Attributive Clauses for example)1). This is a nonsmoking room. Youd better go to the smoking room, whic
35、h is ten meters on your right.2). The boy who is unable to finish his work on time felt a bit sorry for himself.3). Tom and Jack are the only ones in theirs class who dislike football.4). It sounds impossible that the little boy who looks so shy in classwould be so brave to catch a pick-pocket on bus yesterday.Step 2. Give some examples of Restrictive Attributive Clauses andNon-restrictive Attributive Clauses. Let Ss distinguish which of the following sentences areAttributive Clauses and Non-restrictive Attributives Clauses.Non-restrictive:Lijiang, where I was born , is beautiful.
