小升初数学练习题及答案解析
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篇1:小升初数学练习题及答案解析
小升初数学练习题及答案解析
1.甲骑自行车从A地到B地,每小时行16km,2小时后,乙乘汽车也从A地到B地,每小时比甲多行44km,结果比甲早到1h40min,求A、B两地相距多少千米?
2.东方小学五年级1班有50个学生,其中同时参加音乐兴趣小组和美术兴趣小组的有7人,其余的学生也分别参加了音乐或美术小组。参加音乐兴趣小组人数的2/9与参加美术兴趣小组人数的`1/5相等,问参加音乐兴趣小组的有多少人?
解析:
① v甲=16km/h v乙=16+44=60km/h
前半段按追及问题算:
追及路程△S=甲2小时行的路程=16*2=32km
追及速度△v=v乙-v甲=44km/h
追及时间△t=△s/△v=8/11h
则追上甲时乙行的路程x1=v乙*△t=480/11km
后半段是相离问题
t=1h40min=5/3h
△v=44km/h
乙到达时,甲与B的距离△s=16*(5/3)=80/3km
所以△t=△s/△v=20/33h
x2=(20/33)*60=400/11km
x=x1+x2=80km
②方程解法:
设参加音乐组的有x人则参加美术组的有50-x+7=57-x 人
2/9*x=1/5*(57-x) x=27
算数解法:
根据题意,美术组=10/9*音乐组
一共有(1+10/9)音组-7人,即50人
故音组=(50+7)/(1+10/9)=27人
篇2:小升初数学工程问题练习题及答案解析
小升初数学工程问题练习题及答案解析
1.甲乙两个水管单独开,注满一池水,分别需要20小时,16小时.丙水管单独开,排一池水要10小时,若水池没水,同时打开甲乙两水管,5小时后,再打开排水管丙,问水池注满还是要多少小时?
解:
1/20+1/16=9/80表示甲乙的工作效率
9/80×5=45/80表示5小时后进水量
1-45/80=35/80表示还要的进水量
35/80÷(9/80-1/10)=35表示还要35小时注满
答:5小时后还要35小时就能将水池注满。
2.修一条水渠,单独修,甲队需要20天完成,乙队需要30天完成。如果两队合作,由于彼此施工有影响,他们的工作效率就要降低,甲队的工作效率是原来的五分之四,乙队工作效率只有原来的十分之九。现在计划16天修完这条水渠,且要求两队合作的天数尽可能少,那么两队要合作几天?
解:由题意得,甲的工效为1/20,乙的工效为1/30,甲乙的合作工效为1/20*4/5+1/30*9/10=7/100,可知甲乙合作工效甲的工效乙的工效。
又因为,要求两队合作的天数尽可能少,所以应该让做的快的甲多做,16天内实在来不及的才应该让甲乙合作完成。只有这样才能两队合作的天数尽可能少。
设合作时间为x天,则甲独做时间为(16-x)天
1/20*(16-x)+7/100*x=1
x=10
答:甲乙最短合作10天
3.一件工作,甲、乙合做需4小时完成,乙、丙合做需5小时完成。现在先请甲、丙合做2小时后,余下的乙还需做6小时完成。乙单独做完这件工作要多少小时?
解:
由题意知,1/4表示甲乙合作1小时的工作量,1/5表示乙丙合作1小时的工作量
1/4+1/5)×2=9/10表示甲做了2小时、乙做了4小时、丙做了2小时的工作量。
根据甲、丙合做2小时后,余下的乙还需做6小时完成可知甲做2小时、乙做6小时、丙做2小时一共的工作量为1。
所以1-9/10=1/10表示乙做6-4=2小时的工作量。
1/10÷2=1/20表示乙的工作效率。
1÷1/20=20小时表示乙单独完成需要20小时。
答:乙单独完成需要20小时。
4.一项工程,第一天甲做,第二天乙做,第三天甲做,第四天乙做,这样交替轮流做,那么恰好用整数天完工;如果第一天乙做,第二天甲做,第三天乙做,第四天甲做,这样交替轮流做,那么完工时间要比前一种多半天。已知乙单独做这项工程需17天完成,甲单独做这项工程要多少天完成?
解:由题意可知
1/甲+1/乙+1/甲+1/乙+……+1/甲=1
1/乙+1/甲+1/乙+1/甲+……+1/乙+1/甲×0.5=1
1/甲表示甲的工作效率、1/乙表示乙的工作效率,最后结束必须如上所示,否则第二种做法就不比第一种多0.5天)
1/甲=1/乙+1/甲×0.5(因为前面的工作量都相等)
得到1/甲=1/乙×2
又因为1/乙=1/17
所以1/甲=2/17,甲等于17÷2=8.5天
5.师徒俩人加工同样多的.零件。当师傅完成了1/2时,徒弟完成了120个。当师傅完成了任务时,徒弟完成了4/5这批零件共有多少个?
答案为300个
120÷(4/5÷2)=300个
可以这样想:师傅第一次完成了1/2,第二次也是1/2,两次一共全部完工,那么徒弟第二次后共完成了4/5,可以推算出第一次完成了4/5的一半是2/5,刚好是120个。
6.一批树苗,如果分给男女生栽,平均每人栽6棵;如果单份给女生栽,平均每人栽10棵。单份给男生栽,平均每人栽几棵?
答案是15棵
算式:1÷(1/6-1/10)=15棵
7.一个池上装有3根水管。甲管为进水管,乙管为出水管,20分钟可将满池水放完,丙管也是出水管,30分钟可将满池水放完。现在先打开甲管,当水池水刚溢出时,打开乙,丙两管用了18分钟放完,当打开甲管注满水是,再打开乙管,而不开丙管,多少分钟将水放完?
答案45分钟。
1÷(1/20+1/30)=12 表示乙丙合作将满池水放完需要的分钟数。
1/12*(18-12)=1/12*6=1/2 表示乙丙合作将漫池水放完后,还多放了6分钟的水,也就是甲18分钟进的水。
1/2÷18=1/36 表示甲每分钟进水
最后就是1÷(1/20-1/36)=45分钟。
8.某工程队需要在规定日期内完成,若由甲队去做,恰好如期完成,若乙队去做,要超过规定日期三天完成,若先由甲乙合作二天,再由乙队单独做,恰好如期完成,问规定日期为几天?
答案为6天
解:
由若乙队去做,要超过规定日期三天完成,若先由甲乙合作二天,再由乙队单独做,恰好如期完成,可知:乙做3天的工作量=甲2天的工作量
即:甲乙的工作效率比是3:2
甲、乙分别做全部的的工作时间比是2:3
时间比的差是1份
实际时间的差是3天
所以3÷(3-2)×2=6天,就是甲的时间,也就是规定日期
方程方法:
[1/x+1/(x+2)]×2+1/(x+2)×(x-2)=1
解得x=6
9.两根同样长的蜡烛,点完一根粗蜡烛要2小时,而点完一根细蜡烛要1小时,一天晚上停电,小芳同时点燃了这两根蜡烛看书,若干分钟后来电了,小芳将两支蜡烛同时熄灭,发现粗蜡烛的长是细蜡烛的2倍,问:停电多少分钟?
答案为40分钟。
解:设停电了x分钟
根据题意列方程
1-1/120*x=(1-1/60*x)*2
解得x=40
篇3:经典小升初数学复习练习题及解析
经典小升初数学复习练习题及解析
小学是我们整个学业生涯的基础,所以小朋友们一定要培养良好的学习习惯,数学网为同学们特别提供了小升初数学练习题及解析,希望对大家的学习有所帮助!
1.甲骑自行车从A地到B地,每小时行16km,2小时后,乙乘汽车也从A地到B地,每小时比甲多行44km,结果比甲早到1h40min,求A、B两地相距多少千米?
2.东方小学五年级1班有50个学生,其中同时参加音乐兴趣小组和美术兴趣小组的有7人,其余的学生也分别参加了音乐或美术小组。参加音乐兴趣小组人数的2/9与参加美术兴趣小组人数的1/5相等,问参加音乐兴趣小组的`有多少人?
解析:
① v甲=16km/h v乙=16+44=60km/h
前半段按追及问题算:
追及路程△S=甲2小时行的路程=16*2=32km
追及速度△v=v乙-v甲=44km/h
追及时间△t=△s/△v=8/11h
则追上甲时乙行的路程x1=v乙*△t=480/11km
后半段是相离问题
t=1h40min=5/3h
△v=44km/h
乙到达时,甲与B的距离△s=16*(5/3)=80/3km
所以△t=△s/△v=20/33h
x2=(20/33)*60=400/11km
x=x1+x2=80km
②方程解法:
设参加音乐组的有x人则参加美术组的有50-x+7=57-x 人
2/9*x=1/5*(57-x) x=27
算数解法:
根据题意,美术组=10/9*音乐组
一共有(1+10/9)音组-7人,即50人
故音组=(50+7)/(1+10/9)=27人
本文就是我们为广大同学准备的小升初数学练习题及解析,希望可以为大家的学习起到一定作用!
篇4:小升初英语练习题及答案-解析
小升初英语练习题及答案-解析
一、单项选择
1. The twin brothers look __________, but they are in different __________.
A. the same; class B. same; classes
C. different; class D. the same; classes
2--- __________ Mr. Wang have lunch at school yesterday?
---Yes. He often __________ lunch at school.
A. Does; have B. Do; have C. Does; has D. Did; has
3. I’m 13 years old and Tony is 14. So __________.
A. he’s younger than me B. I’m older than him
C. he’s one year older than me D. I’m as old as him
4. __________ Mary’s mother, this woman or that woman?
A. Who B. Who’s C. Whose D. What’s
5. Shall we go to the music room? I want __________ the piano.
A. play B. see C. to buy D. to play
二、阅读理解
For several years, Americans have enjoyed teleshopping watching TV and buying things by phone. Now teleshopping is starting in Europe. In a number of European countries, people can turn on their TVs and shop for clothes, jewelry, food, toys, and many other things.
Teleshopping is becoming popular in Sweden, for example. The biggest Swedish company sells different kinds of things on TV in 15 European countries, and in one year it made $100 million. In France there are two teleshopping channels, and the French spend about $20 million a year to buy things through those channels.
In Germany, until last year teleshopping was only possible on one channel for 1 hour every day. Then the government allowed more telepshopping. Other channels can open for telebusiness, including the largest American teleshopping company and a 24-hour teleshopping company. German businesses are hoping this new teleshopping will help them sell more things.
Some people like teleshopping because it allows them to do their shopping without leaving thei***omes. With all the problems of traffic in the cities, this is an important reason. But at the same time, other Europeans do not like this new way of shopping. They call teleshopping “junk(垃圾)on the air”. Many Europeans usually worry about the quality of the things for sale on TV. Good quality is important to them, and they believe they cannot be sure about the quailty of the things on TV.
The need fo***igh quality means that European teleshopping companies will have to be different from the American companies. They will have to be more careful about the quality of the things they sell. They will also have to work harder to sell things that the buyers cannot touch or see in person.
1. Teleshopping is_____ in Europe.
A.not popular B.growing
C.not possible D.cheap
2. People like teleshopping because it is_____.
A. American B. cheaper
C. easier D. more popular
3. Some Europeans don‘t like teleshopping because they_____ .
A.don't like to buy things
B.don‘t watch TV
C.believe the things sold on TV are expensive
D.think the things sold on TV are bad quality
4. In Germany, teleshopping may_____ .
A.help businessmen get more money
B.keep the shops open longer
C.have fewer buyers
D.bring better TV programmes
5. The best title of this passage is_____ .
A. American Teleshopping
B.Teleshopping Companies
C.Teleshopping in Europe
D.Teleshopping — Junk on the Air
答案:
一、单项选择
1. D 解析:look the same是看起来一样的意思。但是他们在不同的班级,所以不止一个班级,应该用复数。
2.D 解析:第一句中的Yesterday标志应该用一般过去时,第二句中的often标志要用一般将来时。
3. C 解析:C选项的.意思是他比我年长一岁。
4.B 解析: who's是who is的缩写,表示谁是。。。
5. D 解析:want to do sth表示想要做某事。且句中说的是music room,音乐室应该是弹琴而不是买钢琴。
二、阅读理解
1. B 解析:从第二段第一句可以看出,teleshopping正在变流行,所以应该是growing,正在成长。
2. C 解析:从第四段第一行可以看出答案,喜欢电视购物是因为可以不出门就买到东西,比较方便。。
3. D 解析:从第四段第四行可以看出,人们担心电视上卖的商品的质量。、
4. A 解析:从第三段最后一行可以得出答案。
5. C 解析:本文先讲到电视购物在美国流行了很久,然后介绍了其在欧洲的发展。包括在各国的发展情况以及顾客的担心等。
篇5:小升初英语练习题及答案解析
小升初英语练习题及答案解析二
一、用所给词的适当形式填空
1. --- __________ (not smoke) here.
--- I’m sorry.
---Can you see a sign on the wall? It means “No __________ (smoke)”.
2. Their father __________ (swim) very fast. Look, he __________ (swim) in the sports hall now.
3.---Where’s my camera?
---It __________ (is) on the table a moment ago.
4.__________ (do) Nancy’s brothers usually get up at six?
5. There are a lot of books. Please put __________ (they) into the library.
6. ---What can I do for you?
---I want to have two __________ (glass) of milk.
7. Hearing the __________ (excite) news, the students are getting __________ (excite).
二、阅读理解
In 1834, the clock tower in London was burned down. People planned to buil d a new clock which would be the biggest and the best in the world. So the clock had to be big and keep very good time. Several years later the tower was finished. The people put the big clock in the tower, and made it ring out for the first time on July 11, 1859.
In order to give the big clock a good name, people held a meeting. Someone wanted to call it the Queen of Bells , and someone thought Victoria was good . At last, a man named Benjamin Hall stood up. He was a big man. Before he started to speak, someone shouted, “Why not call it Big Ben?” Everybody laughed and agreed with him.
From then on, Big Ben became its name. And it also became a famous building of London. People all over the world write to Big Ben. They even send bottles of oil to help keep Big Ben running. Big Ben is not only a clock but also a dear friend of people.
( ) 46. Big Ben’s birthday is __________.
A. July 11, 1854 B. July 11, 1834
C. July 11 1859 D. July 11, 1852
( ) 47. How did Big Ben get its name?
A.Benjamin Hall gave it the name.
B.Big Ben got its name because of a joke.
C.Big Ben got its name from the Queen of the UK
D.Victoria gave it the name.
( ) 48. “Keep very good time” means ___________
A.have a good time
B.show people the correct time.
C.keep running
D.be made in time
( ) 49. Which of the following is NOT true?
A.People all over the world look upon Big Ben as their friends.
B.People all over the world even send oil to Big Ben.
C.People think Big Ben will reply their letters.
D.People think Big Ben is the biggest and the best clock in the world.
( ) 50. Benjamin Hall is ___________.
A. a man who built Big Ben
B. a man who was always very funny
C.the man who burnt down the old clock
D.a man who attended the meeting which was held to make a name for the big clock
一、用所给词的适当形式填空
1. Don't smoke, somking 解析:前半句是祈使句,变否定时加主动词do,后半句是标志的习惯译法,也可以理解为No后面加名词或名词词性的形式,即动名词形式。
2. swims, is swimming 解析:前半句表示状态,用一般现在时,且由于主语是爸爸,用动词单三形式;后半句有look这个时间标志,用现在进行时。
3. was 解析:最后的时间标志词,a moment ago应该用一般过去时。
4. Do 解析:主语是nancy's brothers是复数,助动词用DO。
5. them 解析:本题考查人称代词用法,本代词作put的宾语,用人称代词的宾格。代的是books用复数them.
6. glasses 解析:本题考查不可数名词表个体时,要用单位名词,在表示复数时将单位名词变复数。
7. exciting, excited 解析:exciting指(物或事件)让人觉得兴奋;excited指(人)兴奋的。
二、阅读理解
1. C 解析:本题从第一段最后一句便可得知答案。
2. B 解析:本题从第二段最后一句可推断出答案。
3. B 解析:本题是推断意思的题目,是阅读理解题中的难点。这类推断短语意思的题目要通读划线部分整句及前后一句基本上就可以得出答案。前一句提到人们希望这个钟应该是'biggest and the best',这与后文的句子是对应的。Big对应biggest, Keep very good time与the best对应。对clock而言,the best就应该是时间很准,所以选B。这类题目一般都直接看不出意思,要通过上下文判断。
4. C 解析:本题为判断正误题,而且选的是错误的选项,应该把每个选项都看过,逐一排除。文中提到人们写信给big Ben但并没提到人们希望能收到回信,所以C选项错误。
5. D 解析:本题通过通读二三段可得出答案。
篇6:小升初英语虚拟语气练习题和答案解析
小升初英语虚拟语气练习题和答案解析
1.i would have come earlier ,but i ___that you were waiting.
A.didnt know B.hadnt known C,wouldnt know Dhavent known
2.had she found it ,she ____it
A.would have sent B.sent C.should send D.send
3.id rather that you ___right away
A.leave B.left C.should leave D.will leave
4.it was a pity that he ____so careless.
A.is B.was C.should be D .were
1.A 本句是虚拟语气和真实语气的混合,逗号前面那句是虚拟语气,后面那句是真实语气,所以选一般过去时。句意:(我要是早知道你在这等我,)我就来早一些了,但是我并不知道你一直在等我。事实上我并没有来早,但是不知道你在等我是真实的。
2.A 逗号前那句其实是if从句,用的'是倒装结构,也可以是if she had found it
本句是对过去情况的虚拟,从句用过去完成时,主句用would+have done
3.A would rather 句后用动词原形表示虚拟
4.D it在这里是形式主语,真正的主语是后面的that从句,这也是虚拟语气的一个句型,但是要用过去式表示虚拟,并且be动词一律用were。还有行为动词的比如:Its time you went to bed.
篇7:小升初英语练习题与答案解析
小升初英语练习题与答案解析
一、选词短文填空
use answer owners hear idea helpful from(从这些词中选择)
We can often see dog taking their dogs for a walk. But have you of taking penguins go out for a walk in line every day. It is said that this can make them happy and stop them being homesick. The penguins in this zoo didn’t eat well and were not kind to workers when they first came to the zoo, maybe they were not to the life in the zoo. So the zookeepers came up with this good They let them walk just as they did in South Pole(南极). Now, all these penguins have become happy.
二、单选
1. Wang Ping is quite good at English. He decides to take up ________ foreign language.
A. the other B. a second C. the second D. other
2. ________ has read the book.
A. Many a student B. Many a students
C. A many students D. A few student
3. -- ________ is the price of this pair of shoes?
--The price is ________. It’s only 60 yuan for each.
A. What; expensive B. How much; high
C. How much; cheap D. What; low
4. The family ________ TV when we got there.
A. are watching B. were watching C. is watching D. was watching
5. The farmers ________ 5 000 new words by the end of last year.
A. have learnt B. learnt C. would learn D. had learnt
6. -- ________?
--I was a waiter in a hotel.
A. What did you do last year B. Where did you work last year
C. How were you last year D. How did yon work last year
7. --The radio is too noisy. ________, please.
--All right. I’ll do it.
A. Turn it off B. Turn it on C. Open it D. Close it
8. You’d better ________ this radio; it can’t receive short-wave programmes ________.
A. not to use; clear B. not use; clear
C. not use; clearly D. not to use; clearly
9. --Look, Mum! I got the first prize in the physics competition today.
--Congratulations! I am very ________ what you’ve done.
A. angry with B. pleased with C. afraid of D. sorry for
10. The report that he ________ was ________.
A. did; successfully B. had; successfully
C. made; a success D. made; success
答案
一、选词短文填空
Keys: 1. owners 2. heard 3. from 4. used 5. idea
二、单选
1. B 解析:一般说来,序数词如first,second等前面要加定冠词the,但是,表示“又一”,“再一”时,序数词前加不定冠词(a an),是 a second,a third的形式.本题翻译为,王平很擅长英语,他决定再学一门外语,再一 ,又一,用a second.
2.A 解析:many a +可数名词单数,谓语也用单数,但意思翻译为许多的。C选项没有这种用法,D中student要加s,而且如果选D,题干中的.动词用复数,是have而不是has.
3.D 解析:价格的提问方法1,what is the price? 2.how much is it ?,两者千万不要混淆。
4.B 解析:主从句时态要一致,when后是过去时,排除AC,family这里指的是家人,复数,选B。
5.D 解析:过去完成时的时间标志,by the end of last year.
6.A 解析:情景问答,回答是我在宾馆当服务员,可知,选A。
7.A 解析:turn on/off应用于有开关物品的开关.open、close指其他物品开关,开收音机,有开关用turn on /off。从题意看,太吵了,所以是关掉。
8.C 解析: You’d better的用法是 You’d better do / You’d better not do,排除AD,后空用副词修饰receive.
9. B 解析:词意辨析,angry with生气 B. pleased with因、、高兴 C. afraid of害怕 D. sorry for为、、抱歉
10.C 解析:首先,后面一空,was 是be 动词的过去式,be 要和形容词,名词等搭配,排除AB.此题成功可以表示为,successful/a success.
篇8:小升初数学练习题
小升初数学练习题整理
【二年级】
课内知识:两位汽车驾驶员,要平分12kg的大桶汽油,眼下身边只有能装5kg和9kg的两只空桶,怎样倒才能平分这此汽油?
课外趣题:学校门前有条长100米的马路,马路两侧一共种了42棵树,每侧相邻两棵树之间的距离都相等,而且马路的两端都种了。请问:相邻两棵树之间的距离是多少米?
【三年级】
课内知识:在1,2两数之间,第一次写上3;第二次在1,3之间和3,2之间分别写上4,5,得到 1 4 3 5 2 。以后每一次都在已写上的两个相邻数之间,再写上这两个相邻数之和。这样的过程共重复了6次,那么所有数的和是多少?
课外趣题:先观察下面各算式,再按规律填数。
9×9+7=88
98×9+6=888
987×9+5=8888
98765×9+___=888888
__________×9+1=_____________
【四年级】
课内知识:甲有5块糖,乙有12块糖。每操作一次是由糖多的人给糖少的人一些糖,使得糖少的人的糖数增加一倍。经过次这样的操作后,两个人的糖数分别是多少?
课外趣题:用1—7这七个数码组成三个两位数和一个一位数,并且使这四个数的和等于100。在满足要求的答案中,最大的数最大可能是多少?最小的两位数最小可能是多少?
【五年级】
课内知识:1到20这20个数中,至少任取多少个数,必有两个数,其中一个数是另一个数的倍数。
课外趣题:用1~8这八个数字组成四个两位数,并使这四个数的和等于144。这四个数中最小数与最大数的乘积最小是多少?
解答:
【二年级】
课内知识:两位汽车驾驶员,要平分12kg的大桶汽油,眼下身边只有能装5kg和9kg的两只空桶,怎样倒才能平分这此汽油?
解答:先把5 kg的空桶装满油倒入9 kg的空桶,再把5 kg的空桶装满油倒入9 kg的桶中,这时5 kg的桶中还剩下1 kg的油。把满满的9 kg油倒回大油桶,再把5 kg的桶中剩下的1 kg油倒入9 kg的油桶,最后用5 kg的桶装满油倒入9 kg的油桶,这时就把12 kg油平均分成了2份,即每份6 kg.
课外趣题:学校门前有条长100米的马路,马路两侧一共种了42棵树,每侧相邻两棵树之间的距离都相等,而且马路的两端都种了。请问:相邻两棵树之间的距离是多少米?
解答:42÷2=21(棵) 100÷(21-1)=5(米)
【三年级】
课内知识:在1,2两数之间,第一次写上3;第二次在1,3之间和3,2之间分别写上4,5,得到 1 4 3 5 2 。以后每一次都在已写上的'两个相邻数之间,再写上这两个相邻数之和。这样的过程共重复了6次,那么所有数的和是多少?
解答:原来两数之和:1+2=3;操作一次:1+3+2=6=3+3;操作2次:1+4+3+5+2=15=3+3+9;操作3次:1+5+4+7+3+8+5+7+2=42=3+3+9+27;......规律是,操作n次,和为 ,所以,操作6次的和为 =1095。
课外趣题:先观察下面各算式,再按规律填数。
9×9+7=88
98×9+6=888
987×9+5=8888
98765×9+___=888888
__________×9+1=_____________
解答:3;9876543,88888888
【四年级】
课内知识:甲有5块糖,乙有12块糖。每操作一次是由糖多的人给糖少的人一些糖,使得糖少的人的糖数增加一倍。经过2009次这样的操作后,两个人的糖数分别是多少?
解答:(5,12)→(10,7)→(3,14)→(6,11)→(12,5)→(7,10)→(14,3)→(11,6)→(5,12),8次一循环。2009÷8=251……1,所以最后甲有10块,乙有7块。
课外趣题:用1—7这七个数码组成三个两位数和一个一位数,并且使这四个数的和等于100。在满足要求的答案中,最大的数最大可能是多少?最小的两位数最小可能是多少?
解答:加数数字和为28,结果数字和为1,28-1=27,说明有三个进位,那么个位数字相加一定为20,十位数字相加一定为8。8=1+2+5=1+3+4,所以最大的数最大可能为57,最小的数可能为12。
【五年级】
课内知识:1到20这20个数中,至少任取多少个数,必有两个数,其中一个数是 另一个数的倍数。
解答:根据题目所要求证的问题,应考虑按照同一抽屉中,任意两数都具有倍数关系的原则制造抽屉。把这20个数按奇数及其倍数分成以下十组,看成10个抽屉:
{1,2,4,8,16},{3,6,12},{5,10,20},{7,14},{9,18},{11},{13},{15},{17},{19}。
从这10个数组的20个数中任取11个数,根据抽屉原理,至少有两个数取自同一个抽屉.由于凡在同一抽屉中的两个数都具有倍数关系,所以这两个数中,其中一个数一定是另一个数的倍数。
课外趣题:用1~8这八个数字组成四个两位数,并使这四个数的和等于144。这四个数中最小数与最大数的乘积最小是多少?
解答:13+28+47+56=144,13×56=728
篇9:小升初数学练习题参考
小升初数学练习题参考
(一)典型例题
例1. 有一个窗框长1米60厘米,准备安装7根铁栏杆,栏杆的距离是多少厘米?
分析与解答:
观察下图不难发现,7根铁栏杆把窗框平均分成8段,我们只要把1米60厘米平均分成8份就可以了。
(1)先求有多少个间隔?
7+1=8(个)
(2)再求栏杆间的距离
1米60厘米=160厘米
160÷8=20(厘米)
答:栏杆的距离是20厘米。
例2. 时钟5点钟敲5下,8秒钟敲完,那么10点钟敲10下,需要多少秒?
分析与解答:
时钟5点钟敲5下,其中有4个间隔,4个间隔用8秒钟的时间,就可以求出每一个间隔所用的时间。然后再想,10点钟敲10下,有9个间隔,就可以求出所需要的时间了。
(1)先求5下有几个间隔
5-1=4(个)
(2)再求每一个间隔的时间
8÷4=2(秒)
(3)再求10下有几个间隔
10-1=9(个)
(4)最后求需几秒钟
2×9=18(秒)
综合算式:8÷(5-1)×(10-1)=18(秒)
答:需要18秒钟。
例3. 在一个正方形池塘四周栽树,四个顶点各栽一棵,这样每边都栽有25棵,如果每相邻两棵之间相距2米,这个正方形池塘的周长有多少米?
分析与解答:
这道题有两种解答方法,一种是先求一共有多少棵树,再求周长;另一种是先求正方形的边长,再求周长。
解法一:
(1)先求一共有多少棵树
25×4-4=96(棵)
或:(25-1)×4=96(棵)
(2)再求池塘的周长
2×96=192(米)
解法二:
(1)先求池塘的边长
2×(25-1)=48(米)
(2)再求池塘的周长
48×4=192(米)
答:池塘的周长有192米。
例4. 长3米的钢管,从一端开始,先30厘米锯一段,再20厘米锯一段,这样长短交替锯成小段,可锯成30厘米长的有多少段?20厘米长的.有多少段?若每锯一段用8分钟,锯完一段休息2分钟,全部锯完需用多少分钟?
分析与解答:
先把3米换算成300厘米,先可以求出把300厘米的长的木棍锯成50厘米的一段,再把每一个50厘米锯成2段,需要6次,共锯11次,休息10次。
3米=300厘米
20+30=50(厘米)
300÷50=6段
6×2-1=11(次)(锯11次,休息10次)
11×8+10×2=108(分钟)
答:锯成30厘米的共6段,锯成20厘米的6段,锯完共需108分钟。
(二)试一试,独立完成
1. 有一个窗框长2米,准备在窗框中间等距离地装9根铁栏杆,相邻的两根铁栏杆距离是多少厘米?
2. 在长90米的跑道两侧插14面彩旗,每相邻两面粉旗之间长多少米?
3. 在小河的一旁,从头到尾要植561棵柳树,已知每隔3米植1棵,那么这条小河长多少米?
4. 在一条长5千米的公路一侧安电线杆,每隔50米安一根,连两端在内一共需装多少根?
(三)解决生活中实际问题
1. 一条路的一侧有37棵树,两树的间隔是5米,现在路的一侧以6米的距离安装路灯,共需要多少盏灯?
2. 把一根木头锯成10段,每锯一段需用7分钟,需几分钟?
3. 一座15层楼,每层的台阶数都相等,小红从一层到3层共走了48个台阶,小红从一层走到15层共需迈多少台阶?
【小升初数学练习题及答案解析】相关文章:
10.小升初数学应用基础练习题






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