小学四年级奥数教程-数的整除性(二).doc

数的整除性（二）这一讲主要讲能被11整除的数的特征。一个数从右边数起，第1，3，5，位称为奇数位，第2，4，6，位称为偶数位。也就是说，个位、百位、万位是奇数位，十位、千位、十万位是偶数位。例如9位数768325419中，奇数位与偶数位如下图所示：能被11整除的数的特征：一个数的奇数位上的数字之和与偶数位上的数字之和的差（大数减小数）如果能被11整除，那么这个数就能被11整除。例1 判断七位数1839673能否被11整除。分析与解：奇数位上的数字之和为1363=13，偶数位上的数字之和为897=24，因为24-13=11能被11整除，所以1839673能被11整除。根据能被11整除的数的特征，也能求出一个数除以11的余数。一个数除以11的余数，与它的奇数位上的数字之和减去偶数位上的数字之和所得的差除以11的余数相同。如果奇数位上的数字之和小于偶数位上的数字之和，那么应在奇数位上的数字之和上再增加11的整数倍，使其大于偶数位上的数字之和。例2 求下列各数除以11的余数：（1）41873； （2）296738185。分析与解：（1）（483）（17）11=71107，所以41873除以11的余数是7。（2）奇数位之和为26315=17，偶数位之和为978832。因为1732，所以应给17增加11的整数倍，使其大于32。（17+112）-327，所以296738185除以11的余数是7。需要说明的是，当奇数位数字之和远远小于偶数位数字之和时，为了计算方便，也可以用偶数位数字之和减去奇数位数字之和，再除以11，所得余数与11的差即为所求。如上题（2）中，（32-17）1114，所求余数是11-4=7。例3 求除以11的余数。分析与解：奇数位是101个1，偶数位是100个9。（9100-1101）11=79911=727，11-7=4，所求余数是4。例3还有其它简捷解法，例如每个“19”奇偶数位上的数字相差9-18， 奇数位上的数字和与偶数位上的数字和相差899=8911，能被11整除。所以例3相当于求最后三位数191除以11的余数。例4 用3，3，7，7四个数码能排出哪些能被11整除的四位数？解：只要奇数位和偶数位上各有一个3和一个7即可。有3377，3773，7337，7733。例5 用19九个数码组成能被11整除的没有重复数字的最大九位数。分析与解：最大的没有重复数字的九位数是987654321，由（97531）-（8642）5知，987654321不能被11整除。为了保证这个数尽可能大，我们尽量调整低位数字，只要使奇数位的数字和增加3（偶数位的数字和自然就减少3），奇数位的数字之和与偶数位的数字之和的差就变为532=11，这个数就能被11整除。调整“4321”，只要4调到奇数位，1调到偶数位，奇数位就比原来增大3，就可达到目的。此时，4，3在奇数位，2，1在偶数位，后四位最大是2413。所求数为987652413。例6 六位数能被99整除，求A和B。分析与解：由99=911，且9与11互质，所以六位数既能被9整除又能被11整除。因为六位数能被9整除，所以A+2+8+7+5+B22+A+B应能被9整除，由此推知AB5或14。又因为六位数能被11整除，所以（A85）（27B）A-B4应能被11整除，即A-B+4=0或A-B+4=11。化简得B-A4或A-B7。因为A+B与A-B同奇同偶，所以有在（1）中，A5与A7不能同时满足，所以无解。在（2）中，上、下两式相加，得（BA）（B-A）144，2B18，B=9。将B=9代入AB=14，得A5。所以，A=5，B9。练习61为使五位数6295能被11整除，内应当填几？2用1，2，3，4四个数码能排出哪些能被11整除的没有重复数字的四位数？3求能被11整除的最大的没有重复数字的五位数。4求下列各数除以11的余数：（1）2485； （2）63582； （3）987654321。5求除以11的余数。6六位数5A634B能被33整除，求A+B。7七位数3A8629B是88的倍数，求A和B。Class: Name: ( )1. Good morning! !A.Morning ! B.Hello ! C.Hi !( )2. Nice to see you again ! .A.How are you ? B.Nice to see you , too . C.How do you do ?( )3.Good night,mom ! A.Night ! B.Good night ! C.Good evening .( )4.How do you do ? A.How are you ? B.Fine,thanks . C.How do you do ?( )5.How many story books do you have ? A.I have 10. B.I can see 10. C.Thirty yuan.( )6.Do you have new teachers? A.Yes,we do . B.Yes,we dont. C.Yes,we have .( )7.Whos your art teacher ? A.Mr Zhu. B.Miss Zhu. C.Hes tall.( )8.Whats he like? A.Hes tall and strong . B.Yes,he is. C.Mr Zhu.( )9.Is your English teacher young? A.No,she isnt. B.Yes,she is . C.No,she is.( )10. ? Her name is Chen Jie.A.Whats your name ? B.Whats she name ? C.Whats her name ?( )11. ? I like Chinese,math and English.A.What classes do you like? B.What do you like? C.What are you like ?( )12. ? We have English and P.E.A.What do you have on Mondays ? B.What do you have ?C.What do you have on Monday?( )13. ? Its Monday.A.What is it today ? B.What day is it today ? C.What day is today ?( )14. ? I watch TV and do my homework.A.What do you do ? B.What do you do in Mondays? C.What do you do on Sundays ?( )15.May I have a look ? A.Sure.Here you are . B.Look ! C.Here you are .( )16.Our math teacher is Canada.A.from B.in C.at ( )17.I three new teachers.A.has B.am C.have( )18.Whats Chinese teacher like ?A.you B.your C.youre( )19.My P.E.teacher is thin.A.too B.so C.very ( )20.There are days in a week.A.six B.seven C.eight ( )21.There are month(月)in a year(年).A.ten B.eleven C.twelve( )22.I often watch TV Saturday .A.on B.in C.at ( )23.I like P.E. I dont lime music.A.but B.and C.so( )24.This is apple. It is red apple.A.a , a B.an,an C.an, a( )25.What do you like ?A.classes B.class C.classs六年级英语测试题Class: Name: ( )1. How are you ? A.Fine,thanks. B.Yes,it is. C.How are you ?( )2. Nice to meet you ! A.Fine,thank you. B.OK. C.Nice to meet you ,too !( )3. How do you go to school ? A.I go to Canada by plane. B.I go to school by bike. C.What about you ?( )4. How do you go to the USA ? A.I usually go to school by bus. B.I go to England by ship. C.I go by plane.( )5. ? My home is near the post office.A. Where is your home ? B.OK. C.See you then!( )6. See you at 2 oclock. A.See you then ! B.The fifth floor. C.Its easy.( )7. ? You can go by the No.15 bus.A.Its not far. B. How can I get to Zhongshan Park ? C.Sure.( )8. Where is the hospital? A.Next to the cinema. B.Thank you . C.Youre welcome.( )9. Excuse me ,is there a cinema near here ? A.Yes,there is . B.No,its not far. C.Its near the post office.( )10.? ? Its near the post office.A.Yes,there is . B.No,its not far. C. Where is the library? ( )11. ? Its next to the hospital. A. Where is the cinema ,please ? B.Is it far ? C.Go straight.( )12. How can I get to the hospital ? A.Its next to the hospital. B.You can go by the No.201 bus. C.Thank you.( )13.Thank you . A.Thank you . B.OK. C.Youre welcome.( )14. How can I get to the museum? A.Go straight.Then turn left. B.Thank you . C.Its east of the cinema .( )15. Where is the post office ? A.Go straight.Then turn left. B.Thank you . C.Its east of the cinema .( )16. What are you going to do this evening ? A.Im going to the cinema . B.I go to school on foot. C.Yes,it is.( )17. Is it far ? A.No,it is . B.Yes , it is . C.Yes,it isnt.( )18. do you go to school ?A.What B.Where C.How( )19. I go to school bike.A.on B. by C.get( )20. Can I go foot ?A.by B.at C.on( )21.How can I to the post office ?A.near B. get C.for( )22. me.A. Excuse B. How C.next ( )23. birthday to you !A. After B.Happy C.First( )24. The hospital is the left.A. at B.in C.on ( )25. is the bookstore ?A.Where B.How C.When 四年级英语测试题Class: Name: ( )1.Good afternoon ! A.Hello! B.Hi ! C.Afternoon !( )2.Nice to see you again ! A.How are you ? B.Hello ! C.Nice to see you , too.( )3.Good night,moom ! A.Good evening ! B.Good night ! C.Night !( )4.How are you ? A.Fine,thank you . B.I am 10. C.Nine .( )5.How do you do ? A.Fine ,Thank you . B.How are you ? C.How do you do ?( )6.How old are you ? A.How are you ? B.I am 11. C.I have 11.( )7. ? I have 23.A.How many books do you have ? B.How many books can you see?C.How many book do you have ?( )8. ? I can see 6.A.How many lights do you have ? B.How many lights can you see ?C.How many light can you see ?( )9.May I have a look ? A.Sure.Here you are . B.Look! C.Sure.Here are you .( )10. ? 50 yuan. A.How much is this schoolbag ? B.How many is this schoolbag ?C.How much are this schoolbag ?( )11.Wheres my seat ? A.Its near the door. B.Its on the door. C.Its under the door.( )12.Lets clean the desks and chairs. A.All right ! B.Hello ! C.Its nice .( )13.Whats this ? A.There is a board . B.Its a bee. C.Its bee.( )14. ? My name is Mike.A.Here are you ? B.Whats your name ? C.How do you do ?( )15.Whos the inventor of paper ? A.Chinese people. B.Oh! Great ! C.Hello!( )16.I a student. You a teacher.A.am ,am B.are, are C.am, are ( )17.This a boy.His name Zhang Peng.A.is, is B.am , is C.is , are ( )18.Let clean the fish bowl.A.I B. me C.my ( )19.This is apple.It is red apple .A.an ,an B.a, a C.an, a( )20.We a new classroom.A.are B.have C.has( )21.There a bee in our classroom.A. is B.are C.am( )22. have a new schoolbag. schoolbag is heavy.A.I , my B.I ,My