王磊同学对本校小型柴油机发电机的工作情况进行调查，得出以下数据：每小时耗柴油2.4kg，输出电压220V、输出电流25A

解题思路：（1）烧开同一壶水，需要的热量相同（燃料完全放出的热量相同）；比过去用液化气所用的时间少了（用的质量少了），由Q_放=mq可知天然气的热值高；
（2）知道水的质量、水的比热容、水的初温和末温，利用吸热公式Q_吸=cm△t求水吸收的热量．

（1）烧开一锅水比过去他们家用液化气所用的时间少了，是因为天然气的热值高；
（2）水吸收的热量：
Q_吸=cm△t=4.2×10³J/（kg•℃）×5kg×（100℃-20℃）=1.68×10⁶J．
故答案为：热值，1.68×10⁶．

点评：
本题考点： 燃料的热值；热量的计算．

考点点评： 本题考查了学生对燃料热值、吸热公式Q吸=cm△t的掌握和运用，要记住1标准大气压下水的沸点（100℃）．

Wang Lei will go to America tomorrow

10x-(20-x)5=110 x=14

Dear Wang Lei,
This is Li Hua,I'm very glad for hearing you's going to study in Canada,congeratulations!We are so proud of you.
As a freind who lives in Canada for three years,I get some advices for you.
About accomodation
No doult,the 1st thing after arriving CA is to find a place to stay,you probabely won't to stay in a hotel as you are using yout parents' money.You can contact your school now,see whether they can help.Student apartment is the best choice for new comers.Home stay is also a good choice,some schools have that kind programme,they have a "home stay" list,make sure you get in touch with the house/aparment owner before your trip.You could also google for apartments for sharing in your destination city in CA,try this website:www.51.ca.Good luck.
Abuout language
I know you got 6.5 on IELTS,which means you can survive in CA.What worries me is your oral English,hope your English teacher doesn't have a stronge Chinese accent,otherwise I suggest you to take an oral English training course before your trip.
About money
Least but not last,money is always an issue.I'll not suggest you to take too much cash with you,2000 dollar is enough.The most important thing is to have an international credit card on hand,which will save you a lot of trouble.China Union Pay card is also acceptable in few banks in CA,but not in most of supermarkets.
BTW,make a copy for all your important documents,such as passport,credit card,driver license,emergency contacts info, etc.
Give me a call when your landing date is fixed,your dad gets my number.
Good luck and have a safe trip (BTW,never take China Airline)!

Best Regards,
David Li (Li Hua)

e the same with

∵AB=AC=6cm，∠ABC=30°，
∴∠BAC=120°，BC=6
3 ，A到BC的距离为3．
∴S _扇形BAC =12πcm ² ；
S _△ABC =9
3 cm ² ；
S _半圆BDC =
1
2 π×(3
3 ) 2 =
27
2 π ．
∴S _阴 =S _半圆BDC +S _△ABC -S _扇形BAC = (
3
2 π+9
3 ) cm ² ．

解题思路：假设20题全答对，他应得20×7=140分，但现在只得了74分，少了140-74=66分．因为答错一题不但不得分，而且要扣4分，也就是答错一题要少得11分．因此答错了66÷11=6（题），答对了20-6=14（题）．

20-（20×7-74）÷（7+4）
=20-66÷11
=20-6
=14（题）
答：他答对了14题．
故答案为：14．

点评：
本题考点： 鸡兔同笼．

考点点评： 此题运用了假设法解答盈亏问题，假设全答对，根据分数差求出答错了几题，进而求出答对了几题．

Dear Zhangming ,
I have heard that you will visit you American friend.I will tell you something you must pay attention to.First,you should bring some small gifts,which is very necessary.And second,you must arrive there on time.Lastly,you’d better say that the food is very delicious to him.Wish you have a nice visit.Good luck.
Yours,
Wang lei

I am Wang Lei, today the school Middle school students to participate in organized adult ritual ceremony and invite parents to participate, my father as a parent representative. Ceremony, parents and teachers expressed expectations of students, students pledge to be good citizens. I must learn, admitted to good universities, to repay their parents! It is a huge adaptation for us as well, after the 18- year- old birthday, we are officially an adult with lots of obligation and responsibility. We need to say farewell to our childhood and be ready to get in to the adult world! Look back to the past, we had overcomed millions of difficulties and changed a lot; look forword to the future, there is a wonderful unknown world waiting for us to dicover. And how the road ahead will be like depends on how we fight for it. So don’t be afraid, make it your own advanture! Hello, my adulthood!

细节决定成败.

假设法
假设全部做对
可得20×10=200（分）
每错一题，就会少的10+5=15（分）
他总共少得200-110=90（分）
所以他错了90÷15=6（题）
做对
20-6=14（题）
综合列式为
做错了（20×10-110）÷（10+5）=6（题）
做对了20-6=14（题）
祝你开心
学习进步
新年快乐

解题思路：（1）烧开同一壶水，需要的热量相同（燃料完全放出的热量相同）；比过去用液化气所用的时间少了（用的质量少了），由Q_放=mq可知天然气的热值高；
（2）燃料燃烧，将燃料的化学能转化为内能；
（3）知道水的质量、水的比热容、水的初温和末温，利用吸热公式Q_吸=cm△t求水吸收的热量；
（4）求出了水吸收的热量，知道能量转换效率，利用η=

Q吸

Q放

×100%求燃料完全燃烧放出的热量，再根据Q_放=mq求需要天然气的质量．

（1）烧开一锅水比过去他们家用液化气所用的时间少了，是因为两种燃料的热值不同，天然气的热值高；
（2）天然气燃烧时，可以将天然气的化学能转化为内能；
（3）水吸收的热量：
Q_吸=cm△t=4.2×10³J/（kg•℃）×1.5kg×（100℃-20℃）=5.04×10⁵J；
（4）∵η=
Q吸
Q放×100%，
∴Q_放=
Q吸
η=
5.04×105J
75%=6.72×10⁵J，
∵Q_放=mq，
∴需要天然气的质量：
m′=
Q放
q=
6.72×105J
4.4×107J/kg≈0.015kg．
故答案为：热值；化学；5.04×10⁵；0.015．

点评：
本题考点： 热量的计算；燃料的热值．

考点点评： 本题考查了学生对燃料热值、燃烧实质、吸热公式Q吸=cm△t、燃料完全燃烧放热公式Q放=mq的掌握和运用，要记住1标准大气压下水的沸点（100℃）．

设这双鞋的原价X元.
即（10÷8）X=188
X=188*（10÷8）
X=235
答：这双鞋的原价是235元.

Dear Huang Ming, I'm glad to hear that you have been invited to your American friend's place. I'm sure you will be welcomed.About the things you asked me, I think I can give you some suggestions. When...

解题思路：分别根据科学记数法的表示方法，得出两人的身高可能，进而得出答案．

有这种可能．
理由：∵1.65×10²≈1.7×10²，1.74×10²≈1.7×10²，
∴1.74×10 ²-1.65×10²=9（cm）．
故有可能．

点评：
本题考点： 科学记数法与有效数字．

考点点评： 此题考查了科学记数法的表示方法，以及用科学记数法表示的数的有效数字的确定方法，得出两人身高是解题关键．

20-（20×10-110）÷（10-（-5））
=20-90÷15
=20-6
=14

（1）改装前灯的总功率：P=60W×6=360W=0.36kW，改装前30天消耗的电能：W=Pt=0.36kW×6h×30=64.8kW•h；需较强亮度时：P 1 =60W×6=360W=0.36kW，不需很亮时：P 2 =60W×2=120W=0.12kW，改装后30天消耗的电能：...

Wang Lei thinks his friends should be the same as him.楼主.要跟王磊虾米一样.要说清楚啊 查看原帖

解题思路：假设20题全答对，他应得20×7=140分，但现在只得了74分，少了140-74=66分．因为答错一题不但不得分，而且要扣4分，也就是答错一题要少得11分．因此答错了66÷11=6（题），答对了20-6=14（题）．

20-（20×7-74）÷（7+4）
=20-66÷11
=20-6
=14（题）
答：他答对了14题．
故答案为：14．

点评：
本题考点： 鸡兔同笼．

考点点评： 此题运用了假设法解答盈亏问题，假设全答对，根据分数差求出答错了几题，进而求出答对了几题．

Dear Wang Lei,This is Li Hua, I'm very glad for hearing you's going to study in Canada, congeratulations! We are so proud of you.As a freind who lives in Canada for three years, I get some advices for you.About accomodation
No doult, the 1st thing after arriving CA is to find a place to stay, you probabely won't to stay in a hotel as you are using yout parents' money. You can contact your school now, see whether they can help. Student apartment is the best choice for new comers. Home stay is also a good choice, some schools have that kind programme, they have a "home stay" list, make sure you get in touch with the house/aparment owner before your trip. You could also google for apartments for sharing in your destination city in CA, try this website: www.51.ca. Good luck.Abuout languageI know you got 6.5 on IELTS, which means you can survive in CA. What worries me is your oral English, hope your English teacher doesn't have a stronge Chinese accent, otherwise I suggest you to take an oral English training course before your trip.About moneyLeast but not last, money is always an issue. I'll not suggest you to take too much cash with you, 2000 dollar is enough. The most important thing is to have an international credit card on hand, which will save you a lot of trouble. China Union Pay card is also acceptable in few banks in CA, but not in most of supermarkets.BTW, make a copy for all your important documents, such as passport, credit card, driver license, emergency contacts info, etc.Give me a call when your landing date is fixed, your dad gets my number.Good luck and have a safe trip (BTW, never take China Airline)! Best Regards,David Li (Li Hua)

大侠您好：
芳草茵茵，踏之何忍。
如能帮到您，还请采纳。

wang's bag is behind the chair,rather than beneath the desk

Dear sister:
How are you?I'm very unhappy.I need your help.
I have a problem.I have many friends,and I get on well with them.But one day,one of my friends left his phone,and he thought that I took away his phone.Then he told others about it,so my friends are not as well as before to me.I'm very worry,and don't know what to do.What should I do?Could you give me some advice?
Yours
Looking for help

Dear Wang Lei!Thank you for your email.I would like to tell you something about our summer vacation.In the holiday I went to Beijing with my parents ,where we had a good time .Jia Qian,Huang Fan and Wu Yan went to Center Park and took a lot of photos there.Liu Fan and Guo Wei went to the Phoenix Islands,Sanya and they did something interesting there.Zhang Yue and Kong Ying went to Qingdao and they played beach volleyball with their friends.We all had a good time .What about your holiday Write to me and tell me .I am looking forward to your letter.
Yours.
Wuyan.

是我.

Dear Wang Lei:
Thank you for your email.I would like to tell you something about our summer vocation.I think this summer holiday is very exciting and interesting.
First,I went to the Center Park with my good friends Jia Qian,Huang Fan and Wu Yan.It was so beautiful that we took a lot of photos there.Then I flew to the Phoenix Islands,Sanya in Hainan province with Liu Fan and Guo Wei.How interesting it was to have a swim in the large blue sea!Finally ,Zhang Yue ,Kong Ming and I went to Qing Dao of Shandong province by train.It has a nice and great seaside.There we played beach volleyball with our friends.I really had an enjoyable summer holiday!How about you?
Yours ,
Wu Yan

解题思路：由于张浩得了87分记作-3分，根据正负数表示两种具有相反意义的量，所以王磊得了95分记作-5分，李金得了90分记作0分．

∵张浩得了87分记作-3分，
∴王磊得了95分记作-5分，李金得了90分记作0分．
故答案为：+5分，0分．

点评：
本题考点： 正数和负数．

考点点评： 本题考查了正数与负数：用正负数表示两种具有相反意义的量．具有相反意义的量都是互相依存的两个量．

First of all, you should have enough sleep at night because staying up too late is bad for your health. Second, it doesn’t make sense to compare yourself with others in class because everyone is different from others physically and mentally. More importantly, it is beneficial to develop a positive attitude towards life. Although we attach importance to the College Entrance Examination, it is equally significant to improve our overall qualities. Therefore you should take regular exercise in order to keep fit. I know you are learning under great pressure especially when the College Entrance Examination is drawing near. Only by relieving stress and pressure properly can you make full use of your time and achieve your goal. It’s normal to experience anxieties which motivate us to move forward instead of dragging us down. Just believe in yourself that you can make it. I do hope my advice will be of a little help to you and improve your learning.

烧开一锅水比过去他们家用液化气所用的时间少了，是因为天然气的热值高；
水吸收的热量：
Q _吸 =cm△t=4.2×10 ³ J/（kg?℃）×1.5kg×（100℃-20℃）=5.04×10 ⁵ J．
故答案为：热值，5.04×10 ⁵ ．

黄磊
张平盗窃为A,黄磊为B,发生在午夜前为C,午夜时机房灯未灭为D,灭为-D
由题意得3）若A则D
又由5）知-D为真
则A为假,又由1）知A=-B,则B为真
所以盗窃的是黄磊则黄磊的证词不正确,所以盗窃的是黄磊

设原价 x 元,那么 x * 0.8 = 188
解 x = 235
这件衣服原价是 235 元.

解题思路：假设20题全答对，他应得20×7=140分，但现在只得了74分，少了140-74=66分．因为答错一题不但不得分，而且要扣4分，也就是答错一题要少得11分．因此答错了66÷11=6（题），答对了20-6=14（题）．

20-（20×7-74）÷（7+4）
=20-66÷11
=20-6
=14（题）
答：他答对了14题．
故答案为：14．

点评：
本题考点： 鸡兔同笼．

考点点评： 此题运用了假设法解答盈亏问题，假设全答对，根据分数差求出答错了几题，进而求出答对了几题．

解题思路：烧开同一壶水比过去他们家用液化气所用的时间少了，就说明的天然气的热值高，完全燃烧相同质量的天然气和液化气，天然气燃烧放热多．燃料在燃烧的过程中是将燃料的化学能转化为内能．

烧开同一壶水比过去他们家用液化气所用的时间少了，是因为天然气的热值高．
天然气和液化气在燃烧时都是将本身的化学能转化为内能；
故答案为：热值，化学．

点评：
本题考点： 燃料的热值；能量的相互转化．

考点点评： 本题考查了学生对燃料热值概念的了解与燃料燃烧时额能量转化问题，要知道单位质量的某种燃料完全燃烧放出的热量叫这种燃料的热值．

（1）水吸收的热量：Q 吸 =cm（t-t 0 ）=4.2×10 3 J/（kg•℃）×40kg×（45℃-35℃）=1.68×10 6 J；（2）因为烧开同一壶水吸收的热量相同，同样条件下烧开同一壶水，用天然气比用液化气所用时间短，说明用的...

1．王磊同学像离弦的箭一样向终点冲去。
2．鲸难道不是哺乳动物吗？
3．人们创造奇迹。
4．他不仅扫了地，还擦了玻璃。

解题思路：假设20题全答对，他应得20×7=140分，但现在只得了74分，少了140-74=66分．因为答错一题不但不得分，而且要扣4分，也就是答错一题要少得11分．因此答错了66÷11=6（题），答对了20-6=14（题）．

20-（20×7-74）÷（7+4）
=20-66÷11
=20-6
=14（题）
答：他答对了14题．
故答案为：14．

点评：
本题考点： 鸡兔同笼．

考点点评： 此题运用了假设法解答盈亏问题，假设全答对，根据分数差求出答错了几题，进而求出答对了几题．

You don't have to worry about my life.I live in Wang Lei home now,have a bedroom to herself,his home goods is full so I have been very good,I go to school by bus everyday,great schools,teachers and students are very friendly.There are 36 students in the class,because Alice and I are from the United States,so often help students learn English.

解题思路：（1）烧开同一壶水，需要的热量相同（燃料完全放出的热量相同）；比过去用液化气所用的时间少了（用的质量少了），由Q_放=mq可知天然气的热值高；
（2）知道（1）液体的沸点和气压有关，气压越高，沸点越高，气压越低，沸点越低；
（3）沸点与气压的关系：沸点越高，气压越高．

（1）烧开一锅水比过去他们家用液化气所用的时间少了，是因为两种燃料的热值不同，天然气的热值高；
（2）水吸收的热量：Q_吸=cm△t=4.2×10³J/（kg•℃）×1.5kg×（100℃-20℃）=5.04×10⁵J；
（3）水在标准大气压下沸点是100℃，气压越低，沸点越低，青海玉树水的沸点是80℃，说明当地气压低于标准大气压；
水沸腾时，需要继续吸热，但温度时不变的．
故答案为：热值；5.04×10⁵；低；不变．

点评：
本题考点： 燃料的热值；沸腾及沸腾条件；热量的计算．

考点点评： 本题考查了学生对燃料热值、吸热公式Q吸=cm△t以及沸点与气压的关系，要记住1标准大气压下水的沸点（100℃）．

解题思路：假设20题全答对，他应得20×7=140分，但现在只得了74分，少了140-74=66分．因为答错一题不但不得分，而且要扣4分，也就是答错一题要少得11分．因此答错了66÷11=6（题），答对了20-6=14（题）．

20-（20×7-74）÷（7+4）
=20-66÷11
=20-6
=14（题）
答：他答对了14题．
故答案为：14．

点评：
本题考点： 鸡兔同笼．

考点点评： 此题运用了假设法解答盈亏问题，假设全答对，根据分数差求出答错了几题，进而求出答对了几题．

（1）水吸收的热量：
Q_吸=cm（t-t₀）=4.2×10³J/（kg•℃）×40kg×（45℃-35℃）=1.68×10⁶J；
（2）因为烧开同一壶水吸收的热量相同，同样条件下烧开同一壶水，用天然气比用液化气所用时间短，说明用的天然气质量较少，根据q=[Q/m]可判断放出同样多的热量，质量越少的热值越大，可见天然气的热值比液化气的热值大．
故答案为：1.68×10⁶；热值．

To tell the truth，Doing exercise will keep your body and your mind in a healthy state. I think ....do sport for one or two hours everyday to improve the efficiency of your study. 给你个链接。

原创~ 楼主分数好少啊,看你在线等才帮你翻译的.
My name is Wang Lei, I come from the Honghu, HuBei province . I am engaged in the correspondence work for 20 years and the design for two years. Therefore, I have rich working experience in the communications engineering design, supervision and construction. Besides, I have three years working abroad experience. I am healthy. Also, have strong sense of responsibility and good leadership skills. That's all, thank you!

Dear Editor: Presently,students have fallen in love with pop music,However,most of the parents disagree with them.In their opinion,pop music will track children's feeling,and it will also be bad for study.So,it is not so good to have a perferrence in them.When it comes to students' opinion,they arguing that listening to pop music will help relax themselves.It really take a good part in life,it can recall our happiness and lucky sence.As far as I am concerned,I think if students can choose healthy music,and they can control proper time to enjoy music,it won't be a bad idea.

解题思路：开始时，水中上下温度不同，热胀冷缩占主导因素；沸腾后，水中温度相同，液体压强占主要因素．

开始时，水还没有沸腾，上部的温度低，气泡遇冷收缩；当水沸腾后，全部的水都升至100℃，蒸气泡上升过程中，所受外部压强减小，所以逐渐变大．
故答案为：减小；增大．

点评：
本题考点： 沸腾及沸腾条件．

考点点评： 本题考查水的沸腾实验的灵活应用与变通，读懂题意，根据常识灵活变通是解决此类问题的关键．

解题思路：（1）烧开同一壶水，需要的热量相同（燃料完全放出的热量相同）；比过去用液化气所用的时间少了（用的质量少了），由Q_放=mq可知天然气的热值高；
（2）知道水的质量、水的比热容、水的初温和末温，利用吸热公式Q_吸=cm△t求水吸收的热量．

（1）烧开一壶水比过去他们家用液化气所用的时间少了，是因为天然气的热值高；
（2）水吸收的热量：
Q_吸=cm△t=4.2×10³J/（kg•℃）×1.5kg×（100℃-20℃）=5.04×10⁵J．
故答案为：热值；5.04×10⁵J．

点评：
本题考点： 燃料的热值；热量的计算．

考点点评： 本题考查了学生对燃料热值、吸热公式Q吸=cm△t的掌握和运用，要记住1标准大气压下水的沸点（100℃）．

出的他平常用的时间 t=3千米/15千米每小时=12分钟.
再算出他这次前1千米所用时间 t=1千米/10千米每小时=6分钟
这时候路还有2千米,时间只有6分钟了(0.1小时）.如果他不想迟到的话.速度=2千米/0.1小时=20千米每小时.
所以答案：20千米/小时

Hello,Peter !How are you now It is a long time since we last saw each other.I am going well with everything except that I met with a traffic accident recently.That day I was riding my bike on the road and when I was trying to cross the road ,a taxi hit me down .But fortunately I was not badly hurt so I was sent to the hospital at once.Now I have recovered and gone back to school.The final exam is coming and I am preparing for it .I think in a month we can enjoy the holidays and I hope you can come to our country for a visit .I am looking forward to seeing you !
Yours.
Wanglei.