梳理数学知识作文450字【一】
1、改写以“万”或“亿”为单位的`数的方法。
以“万”为单位，就要把末尾的四个0去掉，再添上万字;以“亿”为单位，就要把末尾八个0去掉，再添上亿字。
2、改写的意义。
为了读数、写数方便。
总结：本文着重介绍的是“四年级数学知识点：多位数的改写”，“数学知识点多位数的改写”不仅对我们课本上的学习有用，而且我们计算国土面积也是是非常重要的
梳理数学知识作文450字【二】
1. 准确数：在实际生活中，为了计数的简便，可以把一个较大的数改写成以万或亿为单位的数。改写后的数是原数的准确数。 例如把 1254300000 改写成以万做单位的数是 125430 万;改写成 以亿做单位 的数 12.543 亿。
2. 近似数：根据实际需要，我们还可以把一个较大的数，省略某一位后面的尾数，用一个近似数来表示。 例如： 1302490015 省略亿后面的`尾数是 13 亿。
3. 四舍五入法：要省略的尾数的最高位上的数是4 或者比4小，就把尾数去掉;如果尾数的最高位上的数是5或者比5大，就把尾数舍去，并向它的前一位进1。例如：省略 345900 万后面的尾数约是 35 万。省略 4725097420 亿后面的尾数约是 47 亿。
4. 大小比较
1. 比较整数大小：比较整数的大小，位数多的那个数就大，如果位数相同，就看最高位，最高位上的数大，那个数就大;最高位上的数相同，就看下一位，哪一位上的数大那个数就大。
2. 比较小数的大小：先看它们的整数部分，，整数部分大的那个数就大;整数部分相同的，十分位上的数大的那个数就大;十分位上的数也相同的，百分位上的数大的那个数就大……
3. 比较分数的大小:分母相同的分数，分子大的分数比较大;分子相同的数，分母小的分数大。分数的分母和分子都不相同的，先通分，再比较两个数的大小。
梳理数学知识作文450字【三】
练习一
1.Wedoourhomeworkeveryevening.（改为否定句）
We_________________ourhomeworkeveryevening.对划线部分提问
________________dotheyhaveaclassmeeting?
3.Shecouldhardlyunderstandthispassage.(改为反意疑问句
Shecouldhardlyunderstandthispassage,___________________?
4.Themanagertoldhimhowtogetusefulinformation.(改为否定句
Themanager__________________himhowtogetusefulinformation.
5.Tom’ssistercanspeakEnglishandJapaneseverywell.(改为反意疑问句
Tom’ssistercanspeakEnglishandJapaneseverywell,__________________?
对划线部分提问
__________________helivetwentyyearsago?
7.Samdoessomecleaninginthemorning.(改为否定句
Sam_________do_________cleaninginthemorning.
对划线部分提问
__________________havethestudentsworkedonthesurvey?
9.Yourfatherusedtorideabike.（改成反意问句）
Yourfatherusedtorideabike,_______________?（对划线提问）
_____________________thepopulationofGermany?
11.Mr.Wangwasheshiscaronceamonth.（改为一般疑问句）
Mr.Wang(对划线部分提问
willSusancomebackfromAthens?
13.MyfriendslosttheirwaywhentheyweretravelinginHongKong.(改为一般疑问句
________yourfriends________theirwaywhentheyweretravelinginHongKong?
14.对划线部分提问
________________hasYaoMingbeenintheRocketTeam?
15.Sheputthedigitalcameraonthebedjustnow.(改为否定句
She__________________thedigitalcameraonthebedjustnow.
16.Mark'sflowntoHainanIslandforwinterholidays.(改为反意疑问句
Mark'sflowntoHainanIslandforwinterholidays,__________________?
(专辑.(划线部分提问
_________didSuperGirlZhouBichang_________toVienna?
18.I’vealreadysavedenoughmoneytobuyanewcar.(改为否定句
I________savedenoughmoneytobuyacar________.
19.Lilyusedtohavelongstraighthair.(改为反意疑问句
Lilyusedtohavelongstraighthair,________________?
20.Hehasalreadybeenthere.(改为一般疑问句
__________hebeenthere__________?
21.Theydecidedthattheywouldn'thavethepicnicbecauseofthebadweather.(改为简单句
Theydecided___________________havethepicnicbecauseofthebad
weather.
22.TheEnglishpeoplehardlyevershakehandsbetweenthestrangers.(改为反意疑问句
TheEnglishpeoplehardlyevershakehandsbetweenthestrangers,____________________?
23.Theygrewsomesunflowersintheirgardenlastyear.（改为否定句）
They____________________anysunflowersintheirgardenlastyear.
24.Janedrinksmilkeverymorning.（改为一般疑问句）
_________Jane___________milkeverymorning?（就划线部分提问）
___________map___________toClass4?
26.Youcanchooseonlyoneofthetwo:amini-TVoraDVDplayer.(改为选择疑问句
youwantamini-TVaDVDplayer?
27.Thatdetectivefilmissoamazing.（改为感叹句）
______________________amazingdetectivefilm!
28.Hehassomemoneyleft.（改成否定句）
Hemoneyleft.
29.（划线部分提问）
dothemembersofthefilmsocietymeet?
30.Hismotherknewwhythelittleboywasunhappyallday.(改为一般疑问句
_______hismother_______whytheboywasunhappyallday?
31.Helooksveryfunnywiththathaton.(改为感叹句
______________helookswiththathaton!.对划线部分提问
______________theybuildthisfactory?
33.Ihavealreadyfinishedthetestpaper.（改为否定句）
I________finishedthetestpaper________.
34.Johnsondeniedcheatinginthecompetition.（改为反意疑问句）
Johnsondeniedcheatinginthecompetition,________________?（对划线部分提问）________________thestoryneedtobefunny?
36.Samdoessomecleaninginthemorning.(改为否定句
Sam_________do_________cleaninginthemorning.
对划线部分提问__________________havethestudentsworkedonthesurvey?
38.（对划线部分提问）__________________hashebeenatopfashiondesigner?
39.对划线部分提问
________________willtheymoveintothenewschool?
40.togotothePeople’sSquarebyunderground.(对划线部分提问
_______________didittakeyoutogotothePeople’sSquarebyunderground?
练习二：
1.Goldislessvaluablethandiamond.(保持句意不变
Goldis________________valuableasdiamond.
2.HetoldthechildrentogoandwatchhistankofGhostfish.(改为被动语态Thechildren________________togoandwatchhistankofGhostfish.
3.UnlessIhaveaquietroom,Icannotdoanywork.（保持句意不变）
Icannotdoanywork________I_________haveaquietroom.
4.Themanagerarrivedhereafewminutesago.（保持句意不变）
Themanagerhas_________here________afewminutes.
5.TheywillsendhimtoworkinJapanforoneyear.(改为被动语态
Hewill_________________toworkinJapanforoneyear.
6.Thewordsonthenoticeboardareverysmall.Ican’tseethemclearly.(保持句子原意
ThewordsonthenoticeboardaresmallIcan’tseethem
clearly.
7.Wecansolvetheproblemswiththehelpoftheteacher.(改为被动语态Theproblemscan__________________withthehelpoftheteacher.
8.Wecan’tfinishtheworkinsuchashorttime.(保持原句意思
It’s__________________ustofinishtheworkinsuchashorttime.
9.Wemustkeepthenoiseunder50dbs.(分贝（改成被动语态）
Thenoisemust_______________under50dbshere.
10.Mikedoesn’tlikeclassicalmusic.Billydoesn’teither.（合并成一句）_________MikenorBilly__________classicalmusic.
11.Theroomissodirtythatwecan’tliveinit.（保持句意不变）
Theroomisn’t___________________forustolivein.
12.Nooneknowswhenwewillstarttomorrow.（保持原句意思）
Nooneknowsstarttomorrow.
13.TheSmithswillinvitetheprofessortotakepartintheparty.(改成被动语态totakepartinthepartybytheSmiths.
14.Ifyouarenotbrave,you’llloseyourlastchance.（保持原句意思）
youare’llloseyourlastchance.
15.Theystoremuchinformationinthecomputer.(改成被动语态
Muchinformation________________inthecomputer.
16.Don’tthrowrubbishhereandthere.Ourteachersaidtous.(合并为一句
Ourteachertoldus________________throwrubbishhereandthere.
17.IfJohndoesn’tapologizeforwhathedid,Iwilltelltheteacherabouthisbadbehavior.（保持原句意思）
_______John_______forwhathedid,Iwilltelltheteacherabouthisbadbehavior.
18.Idon'tknowwherewecangrowvegetablesinthecity.(改为简单句Idon'tknow__________________growvegetablesinthecity.
19.PeopleusedtoenjoythemselveschattingonMSNwhenitworkedwell.(保持句意基本不变
Peopleusedto_________alotof_________chattingonMSNwhenitworkedwell.
20.Ifyoudon’timproveyourhandwriting,youwilllosemarksintheexam.(合成同义句
Youwilllosemarksintheexam________you________yourhandwriting.
21.Togofishingisfun.（句意不变）
_____isfun___________fishing.
22.Dickwassoshortthathecouldn’ttouchthetopofthebookshelf.（保持句意基本不变）
Dickwasn’t____________________toreachthetopofthebookshelf.
23.“CanIborrowyourbikeforawhileornot?”（保持句意基本不变）
Tomaskedhissister__________he__________borrowherbikeornotforawhile.
24.Thecouplecouldn’tdecidewhichflattheyshouldchooseatfirst.（保持原句意思）
Thecouplecouldn’tdecidewhichflatatfirst.
25.Meaninglessinformationisdifficultforthelittleboytoremember.（保持原句意思）
isdifficultforthelittleboyremembermeaninglessinformation.
26.Peoplethrowawaymillionsofplasticbagsinourcityeveryday.（改成被动语态）
Millionsofplasticbagsawayinourcity.
27.Shewassocarelessthatshecouldn’tfindthemistakesinhertestpaper.(保持句意基本不变
Shewas______________tofindthemistakesinhertestpaper.
28.WewillholdthenextOlympicGamesinBeijingin2008.（改为被动语态）
ThenextOlympicGameswill______________inBeijingin2008.
29.Theelderlymanpushedthebirdsintotheriver.（改为被动语态）
Thebirds________________intotheriverbytheelderlyman.
30.Dolphinsaresocleverthattheycanfollowtheinstructions.（保持句意基本不变）Dolphinsare________________tofollowtheinstructions.
31.Wecan’tfinishtheworkinsuchashorttime.(保持原句意思
It’s__________________ustofinishtheworkinsuchashorttime.
32.TheyinvitedtheastronautandhiswifetothepartyonChristmasEve.(改为被动语态
Theastronautandhiswife__________________tothepartyonChristmasEve.
33.Thelittlegirldidn’tgotobedunlessthegrandmothertoldherastory.(保持句意基本不变
Thelittlegirldidn’tgotobed_________thegrandmother_________tellherastory.
34.Theplaneissobigthatitcancarry300passengersatonetime.（改为简单句）
Theplaneisbig__________________carry300passengersatonetime.
35.Didtheyknowtheanswertothequestion?Ididn’tknow…(合并为一句Ididn’tknow________theyhad________theanswertothequestion.
