4只猫在4分钟内捉4老鼠.照这样计算,4分钟内捉10老鼠,需要多少只猫?

1.404乘以10*-10个／分

怎么介绍,你总该给点参考资料吧,我们又不是你肚子里的蛔虫,哪里知道你亲戚朋友的喜好呀!

（1）当0≤x≤4时，y=（20÷4）x=5x，
当4＜x≤12时，设解析式为y=kx+b（k≠0，k，b为常数），
依题意得

4k+b＝20
12k+b＝30，
解之得：k=[5/4]，b=15，
∴y=[5/4]x+15；

（2）根据图象知道：
每分钟进水20÷4=5升、
每分钟出水[（12-4）×5-（30-20）]÷（12-4）=[15/4]升；

（3）∵12分钟以后只出水不进水，
∴30÷[15/4]=8分钟，
∴8分钟将水放完，
∴函数解析式为y=30-[15/4]（x-12）=-[15/4]x+75，
图象如图：

已知,v摩=108km/h=30m/s,t=4min=240s,s0=1000m,v汽=25m/s.
假设摩托车先加速t1时间,后匀速运动t2时间,4分钟内摩托车的位移为
s摩=v摩t1/2+v摩t2
t1+t2=t
汽车的位移为
s汽=v车t
由已知可知s摩=s汽+s0
解得t1=40/3s
则加速度a=v摩/t1=2.25m/s^2

1.
当X＜4,y＝2X
当4≤x ≤12,y＝6＋12X
当x＞12,y＝18－12X
2.
8÷4＝2 升分 这是每分钟进水量
[12－4]×2－12＝4 升 这是8分钟的出水量
4除8等于12 [升分] 每分钟的出水量

一只家用电能表标着3000转/小时,这表示每消耗1KW.H的电能.现在室内只接了一只灯泡,测出转盘4分钟内转了12转,利用这些数据算出灯泡在这期间消耗的电能是（ 0.004 ）KW.H=（ 1.44x10^4 ）J灯泡功率是（ 60 ）W.如果电能表标有“220V 5A",最多能安装“220V 60W”的电灯（ 18 ）盏.若电灯平均每天开2小时,（30天）要消耗（ 64.8 ）度电

（1）求0≤x≤4时,随变化的函数关系式
V=5x (0≤x≤4)
（2）求4≤x≤12时,随变化的函数关系式
V=1.25(x-4)+20=1.25x+15 (4≤x≤12)
（3）每分钟进水,出水各为多少升?
进水：20升/4分钟=5升/分钟
出水：（5升/分钟×12分钟－30升）÷（12分钟-4分钟）=3.75升/分钟
每分钟进水5升,出水3.75升

由电能表的标度可知，电能表每转1500转为1度，10转所消耗的电能为：
W=
10r
1500r/kw•h =
1
150 kw•h ，
消耗这些电能所用的时间t=4min=
1
15 h
则台灯的功率P=
W
t =

1
150 kw•h

1
15 h =0.1KW．
故答案为：0.1kw．

已知：a÷4分之1＝b÷3分之1＝c×5分之1,并且a、b、c都大于0.
即A×4=B×3=C/5,
A=B×3/4=C/20
则：A＜B＜c

在青海省西部一个极度缺水的地方,每个人每天只能用三斤水.一天,一头老牛挣脱缰绳挡在了运水车前.任凭驾驶员怎样赶它,老牛都不为所动.牛的主人用长鞭抽在牛背上,牛凄厉地叫着,感动了所有人.于是运水战士破例给了老牛半盆水,而老牛呼唤小牛来喝水.最后母子眼中充满了泪水.

哈哈,还是你,这次两个都帮你回答了
1、省钱的主意
A:excuse me,can I ask you some for some questions?
B:all right,just do it.
A:thank you,as a college student,do you have some good ideas about saving money?
B:for me, I just try my best to save as much as I can
A:can you explan it in detail?
B:First,I take work_study programe,it’s not noly a good idea to save money but also can eran money.secondly,with limited money in my pocket,I choose to buy cheap things as much as possible,one way to do that,is team_buying, online team_buying offers huge discounts
A:EN,yes,do you have other good ideas,you can think about some different ways from your friends.
B:oh,let me think..i remember that one of my friends ever sayed he hadn’t planed to find the other half because once having a girlfriend ,it will be meaning to spend money.
A:haha,that’s really a good idea
B:yes,in addition,we can take our most time on our study,and cut down on entertainment.
A:yes,little entertainment means low cost.
B:so what is your opinon of how to save money?
A:basically the same as you have sayed.they are actually wonderful ideas.i want to say that I have ever traveled to many cities where there are my good friends,it is a very good way of saving money in travelling,because friends can acr as free guides and slao offer me free accommodation.meanwhile,it can slso save time and energy.
B:WAOH,that’s so cool.
A:ok,I want to thank you for your nice chat with me and your great ideas.
B:you are welcome.
2、做调查
A: excuse me,can I take up some time of you to do a survey
B:of couse ,with pleasure.
A:thank you.as a college student,what do you think about how to make our campus a better place..
B: The first thing we can do is to make our campus more beautiful. Every one of us may plant a tree in the school, or organize a thorough cleaning on the campus. We can also form a good habit of putting the rubbish in the trashcan.
A:yes,that’s right,a clean and quiet environment is very important for us.
Bl The second thing we can do is to protect the facilities in our school. When we leave the classroom, we should never forget to turn off the light or close the door. We should also develop a good habit not to leave the tap water running or waste any materials in the laboratory class
A:yes,good habit has a very significant influence on us,we shoud also develop our habit studying hard.
B:yes,I hope all of us can make our efforts to make our campus a good place.
A:I hope so. If everyone does one thing for our school, I believe we will turn our school into a better place to study and live in
B:that’s right
A:thank you for your ideas.
B:you are welcome.

1.每分钟进水20÷4=5升、
2.y与x的函数关系式是y=kx+b,把（0,0）（4,20）代入得
{b=020=4k+0
∴k=5,b=0
∴y与x的函数关系式是y=5x（0≤x≤4）
3.设y与x的函数关系式是y=kx+b,把（4,20）（12,30）代入得
{20=4k+b
30=12k+b
∴k= 5/4,b=15
∴y与x的函数关系式是y=﹙ 5/4﹚x+15（4＜x≤12）

一辆摩托车行驶得最大速度为108km/h,现让摩托车从静止出发、要求在4分钟内追上前方相距1千米正以25m/s得速度在平直公路上行驶的汽车、则该摩托车行驶时、至少应具有多大的加速度?
摩托车的最大速度V =108km/h=30m/s,4分钟内前方汽车已前进25×240=6000m,
摩托车以最大速度30m/s走完7000米需要7000/30=233秒,故留给加速的时间可以多于7秒.
设用t₁秒时间加速到30m/s,那么加速度a=30/t₁(m/s²)；
加速段走过的路程S₁=(1/2)at²₁=(1/2)×(30/t₁)t²₁=15t₁(m)；
留给以最高速追赶的时间t₂=240-t₁,
故有等式：(7000-15t₁)/30=240-t₁,解之得t₁=200/15=40/3=13.33秒.
故在4分钟内追上汽车所需要的最小加速度amin=30/(40/3)=90/40=2.25m/s².

1kw*h=3600000J
所以：1200r/kw*h=1200r/3600000J=1r/3000J
W=55r/(1r/3000J)=165000J

既然是初二水平,那你可以编一个自然发音的小话剧,如：
A:Today we learn some phonics.Phonics is the best way in which you can learn English.You are my children.We parents have to choose the best way in which you can learn well.
B:Today,we learn the sound of "c" and "h" together.They sound like "ch".Dick,say it with me.
C-h,ch,ch.
C:C-h,ch,ch.
B:T-c-h,tch,tch.
D:T-c-h,tch,tch.
A:Okay,let's try the ending digraph of "ch".First,we learn the word family of "each".Mary,say it with me.Ea-ch,each.Each,each,each.
D:Ea-ch,each.Each,each,each.
A:P-each,peach.Peach,peach,peach.
D:P-each,peach.Peach,peach,peach.
A:Sit on the bench and finish the peach.
D:Sit on the bench and finish the peach.
A:Okay,let's learn the word family of "atch".A-tch,atch.Atch,atch,atch.
D:A-tch,atch.Atch,atch,atch.
A:The patch does not match.
D:The patch does not match.
A:Oh,I have lots of fun chanting with you.
C&D:Me,too.

解题思路：先根据函数图象求出进水管的进水量和出水管的出水量，由工程问题的数量关系就可以求出结论．

由函数图象得：
进水管每分钟的进水量为：20÷4=5升
设出水管每分钟的出水量为a升，由函数图象，得
20+8（5-a）=30，
解得：a=[15/4]，
故关闭进水管后出水管放完水的时间为：30÷[15/4]=8分钟．
故答案为：8．

点评：
本题考点： 一次函数的应用．

考点点评： 本题考查利用函数的图象解决实际问题和用一元一次方程求出水管的出水量的运用，正确理解函数图象横纵坐标表示的意义，理解问题的过程，就能够通过图象得到函数问题的相应解决．

A：Good morning , B
B: Good morning. How are you?
A: I 'm fine. Thank you. And you ?
B: Fine. Thank you.
A: let me introduce my friend C to you.
B: Nice to meet you.
C: Nice to meet you, too.
B: Where will you go ?
A: We will go to C's home. Today is hisher birthday.
B: Really? Happy birthday .
C: Thank you very much. Do you have time to celebrate my birthday?
B: Of course. If I don't trouble you.
C: I appreciate it. My parents will happy to see you.
On the way to C's home
B: C, what do you do in your spare time?
A: HeShe likes to see the movie very much.
C: Yes, I want to buy ‘The banquet’to see.
B: Oh, what luck! I have just bought this .
I 'd like to give you this film for your birthday.
C: Thank you . This is the special gift for my birthday .

由电能表的标度可知，电能表每转1500转为1度，10转所消耗的电能为：
W=[10r/1500r/kw•h]=[1/150kw•h，
消耗这些电能所用的时间t=4min=
1
15h
则台灯的功率P=
W
t＝

1
150kw•h

1
15h]=0.1KW．
故答案为：0.1kw．

1500r/KWh的意思就是每用KWh(度)电要转1500转.每转1/1500度电.
那么4分钟10转用掉的电就是(1/1500)*10=1/150度电.
每分钟(1/150)/4=1/600度,每小时(1/600)*60=1/10度.

设一道正门1分钟通过x人,一道侧门1分钟通过y人.
2(x+2y)=140
4x+4y=200
解得x=30 y=20
答：一道正门1分钟通过30人,一道侧门1分钟通过20人.
或
(200-140)/2=30人 (140/2-30)/2=20人

The rabbit and the tortoise
龟兔赛跑
背景:在一个大森林里,小动物们快乐地生活着,充满它们的欢声笑语.
旁白:Good morning everyone.I'm a bird .I live in a forest .Now,I will tell you a story about Mr.Tortoise and Miss Rabbit.In a very big forest,there lives many animals,like rabbit ,monkey ,dog,zebra,elephant and hone t Tortoise.Miss Rabbit is very proud of her long legs .Today,an interesting thing is happening.
兔子:Hi!Mr.Tortoise.What are you doing
乌龟:Hi!Miss Rabbit.I am running.
兔子大笑:What Run Just like now Ah,Ah,Ah,You are too slow.I can even walk faster than you run.
乌龟:Miss Rabbit,You are too proud.We should have a race.I believe I can win the match.
兔子:What What A race With you You can win OK.OK.Look at the tall tree.Let me see who can get there first.
乌龟:OK !
兔子:Who will be the winner Of course,It is me.
小猴(大声宣布):The rabbit and the tortoise are going to have a race!
旁白:Many animals hear the news in the forest.They all come to watch the race .
小动物们全部集中,议论纷纷.
小猴:I'm sure the rabbit will win the race!
小鹿:I hope the tortoise will win ..
其他小动物附和着.
小兔对乌龟说:I'm sure I will beat you.Don't cry if you lose.
乌龟回答:Let's wait and see .
小鹿宣布:Ready ,set ,go !
比赛音乐响起.
乌龟和小兔开始赛跑,乌龟慢慢趴,小兔跳的很快.
小动物们:Come on ,Rabbit !
Come on ,Tortoise ,don't give up .
旁白:The rabbit runs very fast .She soon comes to a tall tree .She looks back .
小兔回头看乌龟:The tortoise is so slow .I can't see him now .I'll take a nap under the tree.
小兔在大树下躺下,呼呼大睡.乌龟继续爬着.
斑马跑到乌龟旁边悄悄说:Come on ,Tortoise ,don't give up .
乌龟:Thank you .I see .I'll try my best .
旁白:An hour later ,the tortoise comes to the tree .The rabbit is still sleeping .He runs on an on .
乌龟:How tired,but I can not give up.
小狗:Mr.Tortoise,Come on,Come on.You could be the winner!
小兔醒了,往后看.
小兔:Where is the tortoise Oh my God !
小兔朝前看,乌龟快到终点了.小兔赶紧用最快的速度向终点冲去.
乌龟冲过终点线,与其他小动物一起欢呼.
小动物齐鼓掌欢呼:The tortoise won the race !
乌龟:Oh ,I can't believe it .I won the rabbit !
小兔作害羞状,与乌龟拉起横幅:
Pride comes before a fall.骄兵必败骄兵必败.
小动物们一起说:Pride comes before a fall.骄兵必败

若摩托车在整个过程刚好加速到最大速度,
由V=at得,当t最大时,a最小
即t=240s(即4min),V=30m/s(即108km/h)
可求出a=0.125m/s^2
由S=1/2at^2,将a带入去验证S
可算出S=3600m,可此时汽车在240s内行驶了6000m,所以此情况不符合题意
同理可以推出,摩托车在整个过程未加速到最大速度的情况也不符合题意
所以,可以判断出,摩托车在整个过程中是先加速到最大速度,之后匀速,最终追上汽车
所以,设摩托车行驶的距离为S1,汽车行驶的距离为S2,摩托车加速行驶的时间为T1,匀速行驶的时间为T2,摩托车最大速度为V,汽车速度为v,得
S1=1/2aT1^2+VT2
S2=vT
使摩托车追上汽车,即S1=S2+1000
即1/2aT1^2+VT2=vT+1000
又摩托车最大速度V=aT1,T=T1+T2(T小于等于240s)
代入上式,得
T2=2T1+200
代入T=T1+T2(T小于等于240s),得
T1小于等于40/3s
再由V=aT1得,当T1最大,即T1=40/3时
a最小,为2.25m/s^2

解题思路：（1）摩托车追上汽车，根据位移关系，求出加速度，然后讨论摩托车有无超过最大速度，若超过最大速度，知摩托车先做匀加速直线运动，再做匀速直线运动进行追赶，根据位移关系，从而求出摩托车的最小加速度．
（2）当达到共同速度时，两车相距最远．

（1）假设摩托车一直匀加速追赶汽车，则：
1
2at2＝v0t+s0
代入数据得，a=0.24m/s²．
摩托车追上汽车时的速度：
v=at=0.24×240m/s=57.6m/s＞30m/s
所以摩托车不能一直匀加速追赶汽车，应先匀加速到最大速度再匀速追赶．

1
2at12+vm(t−t1)＝s0+v0t ①
v_m=at₁ ②
①②联立两式解得t1＝
40
3s
则a＝
vm
t1＝2.25m/s2
故摩托车的加速度至少为2.25m/s²．
（2）当两车速度相等时相距最远，设达到共同速度的时间t₂
则t2＝
v
a＝
25
2.25s＝
100
9s
两车相距最远距离△x＝s0+vt2−
v
2t2＝
10250
9m＝1138m
答：（1）该摩托车行驶时，至少应具有2.25m/s2加速度？
（2）摩托车与汽车之间的最大距离为1138m．

点评：
本题考点： 匀变速直线运动的位移与时间的关系；匀变速直线运动的速度与时间的关系．

考点点评： 关于追及问题，抓住两个关系：一是位移关系，二是时间关系，一个临界即速度相等时，然后利用运用匀变速直线运动的公式进行求解即可．

.at=30
把2式带到1式中,划简得:450/a+(240-30a)*30=7050
450/a+7200-900/a=7050
7200-450/a=7050
450/a=150,解得a=3
其中3是刚好能追上时的加速度,根据题意,应该大于等于3,
第2问的关键在于:当两车速度相等时距离最大...
1.at=25
2.Smax=25t+1050-1/2at^2
把a=3带入1中,
得t=25/3
把t=25/3带入2中,
得Smax=625/3+1050-625/6
Smax=1050+625/6=1154.2

解析：假设摩托车一开始就是以30m/s行驶,则摩托车每秒追汽车5m/s
而4分钟内有4×60=240s,则最大可以追240×5=1200m,而汽车在前方1000m
推出摩托车必须要1200-1000=200m内达到最大速度
根据2as=vt²-v得
2a×200=30²-0
a=2.25m/s²
所以得a≥2.25m/s²望采纳

1、我觉得应该是求最小加速度吧,也就是求正好在4分钟的时候追上汽车；随着加速度增大,那么住上汽车的时间就越短,则时间就会小于4分钟.下面的解法是按照最小加速度算的.
首先,如果在整个过程中摩托车的平均速度必须大于25m/s,由于汽车是在进行匀加速运动,所以汽车应该在这4分钟的时间里达到了最高的30m/s.设加速度为a：
15*30/a+(240-30/a)*30=240*25+1000
则a=2.25m/s*s
2、这样的情况就是在乘客可以承受的范围内,以最大的加速度行驶,然后在意这样的最大加速度减速到站,所以应该是,设加速时间为t（则减速的时间也应该为t,总时间是2t）：
0.5*1.4*t*t=560/2
t=20
所以全程40s,最大行驶速度v=1.4t=28m/s

The two pots
There were two pots on the bank of a river.One was made of brass,and the other was made of clay.
When the water rose they both floated off down the river.The earthen pot tried to stay away from the brass one.
So the brass pot cried out,"Fear nothing,friend,I will not hit you."
"But I may come in contact with you," said the earthen pot."If I come too close,whether I hit you or you hit me,I shall suffer for it."
After that the earthen pot floated away.
两口锅
河中漂流着一个瓦锅和一个铜锅.
每当潮涨潮落时,瓦锅就尽量地远离铜锅.铜锅大叫：“别害怕,朋友,我不会撞你的.”
“但是我有可能会和你接触,”瓦锅对铜锅说,“如果我离你太近,无论是你碰到我,或者是我自己不小心碰到你,我都会碎的.”
然后,瓦锅就漂走了.

(1)20/4=5L
每分钟进水5L
(2)(y-30)/(x-12)=(30-20)/(12-4)
4y-120=5x-60
y=(5x+60)/4
(3)设每分钟出水是a
5*8-8a=30-20
a=15/4
y=30-15(x-12)/4
令y=0
那么30-15(x-12)/4=0
120-15x+180=0
x=20分钟
所以当放完水时,是第20分钟

1 The plants seeds in the soil .( seeds 作动词‘ 播种’
2 How do you plant a tree
3 What can you see in the picture
4 It is a sunny day .

（1）由图知每分钟进水20/4=5升.
（2）由图知k=(30-20)/8=5/4且过点(4,20)=>Y=5/4X+15
（3）由（2）k=（进水-出水）*8=10=>每分钟出水15/4即k=-15/4
又过点(12,30)=>Y=-15/4X+75