四年级奥数第五讲_等差数列(二)_学生版

网络精品小说

第五讲 等差数列（二）

解题方法

某些问题以转化为求若干个数的和解决这些问题时先要判断这些数是否成为等差数列，如果是等差数列才可以运用它的一些公式。

在解决自然数的数字问题时，应根据题目的具体特点，有时可考虑将题中的数适当分组，并将每组中的数合理配对，使问题得以顺利解决。

例题1 小王看一本书第一天看了20页，以后每天都比前一天多看2页，第30天看了78页正好看完。这本书共有多少页？

引申

1、文丽学英语单词,第一天学会了3个，以后每天都比前一天多学会1个，最后一天学会了21个。文丽在这些天中共学会了多少个英语单词？

2、李师傅做一批零件，第一天做了25 个，以后每天都比前一天多做2个，第20天做了63个正好做完。这批零件共有多少个？

3、小李读一本短篇小说，她第一天读了20页这个等差数列共有多少项?

例题2 建筑工地上堆着一些钢管(如图所示),求这堆钢管一共有多少根。

网络精品小说

引申

1、一些同样粗细的圆木,像如图所示一样均匀地堆放在一起,已知

最下面一层有70根。一共有多少根圆木？

2、用3根等长的火柴棍摆成一个等边三角形,用这样的等边三角形，按下图所示铺满一个大的等边三角形,如果这个大的等边三角形的底边能放10根火柴棒,那么这个大的等边三角形中一共要放多少根火柴棒?

3、用相同的小立方体摆成如图所示的形状,如果共摆成10层,那么最下面有多少个小立方体?

例题3 有50把锁的钥匙搞乱了,为了使每把锁都配上自己的钥匙,至多要试多少

次?

引申

1、有60把锁的钥匙搞乱了,为了使每把锁都配上自己的钥匙,至多试多少次?

网络精品小说

2、有一些锁的钥匙搞乱了,已知至多要试28次,就能使每把锁都配上自己的钥匙。一共有几把锁的钥匙搞乱了?

3、一辆公共汽车有66个座位,空车出发后,第一站上一位乘客,第二站上两位乘客,第三站上三位乘客,依次类推,第几站后,车上坐满乘客?

例题4 四（1）班45位同学举行一次同学联欢会，同学们在一起一一握手，且每两个人只

引申

1、学校进行书法大赛，每个选手都要和其他所有选手各赛一场。如果有16人参加比赛，一共要进行多少场比赛？

2、在一次元旦晚会上，一共有48位同学和5位老师，每一位同学或老师都要和其他同学握一次手。那么一共握了多少次手？

3、一次朋友聚会，大家见面时总共握手28次。如果参加聚会的人和其余的每个人只握手一次，问参加聚会的共有多少人？

网络精品小说

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 don’t. C.Yes,we have .

( )7.Who’s your art teacher ?

A.Mr Zhu. B.Miss Zhu. C.He’s tall.

( )8.What’s he like?

A.He’s tall and strong . B.Yes,he is. C.Mr Zhu.

( )9.Is your English teacher young?

A.No,she isn’t. B.Yes,she is . C.No,she is.

( )10. ? Her name is Chen Jie.

A.What’s your name ? B.What’s she name ? C.What’s 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.

网络精品小说

A.What do you have on Mondays ? B.What do you have ?

C.What do you have on Monday?

( )13. ? It’s 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.What’s Chinese teacher like ?

A.you B.your C.you’re

( )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 don’t lime music.

A.but B.and C.so

网络精品小说

( )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.class’s

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 o’clock.

A.See you then ! B.The fifth floor. C.It’s easy.

( )7. ? You can go by the No.15 bus.

A.It’s 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.You’re welcome.

( )9. Exc …… 此处隐藏：3288字，全部文档内容请下载后查看。喜欢就下载吧 ……