本题所属标签:计算12十二1314151
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计算(1+12+13+14)×(12+13+14+15)-(1+12+13+14+15)×(12+13+14)的值是()。
a．1
b．14
c．15
d．0
本题所属标签:计算12十二1314151__A
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[优质解答] 计算(1+12+13+14)×(12+13+14+15)-(1+12+13+14+15)×(12+13+14)的值是__。
A．1
B．14
C．15
D．0
本题所属标签:计算12十二1314151__A
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[优质解答] 计算(1+12+13+14)×(12+13+14+15)-(1+12+13+14+15)×(12+13+14)的值是__。
A．1
B．14
C．15
D．0
本题所属标签:阅读浏览理解1412十二1012大量
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| 阅读理解。 |
The doctor pointed to some bones on his desk. "They are a man"s foot bones," he said. "They
were found inside the cave, and I have been examining them. The C14 test shows that they are
about 12,000 years old."
"What is the C14 test" I asked. "It"s a way of finding the age of some things that had been
done long ago. The "C" means carbon and carbon is found in al l living things. It is also found in
the remains of things that lived and died thousands or millions of years ago. Plants and animals
take carb on into their bodies from the air. It stays in their remains."
"Well, there are two kinds of carbon, called carbon 12(C12) and carbon 14 (C14). Both are
taken in together, but in living things C12 is one trillion (1012) times more plentiful (大量的) than
C14. The two kinds are different in one important aspect."
"C14 is radioactive:it gives out rays of energy at a fixed frequency (频率). As it does so, it
changes to C12in 5,600 years. Then in the next 5,600 years, half of the remaining C14 becomes
C12 and so on. We say that C14 has a half-life (半衰期) of 5,600 years."
"You must have found some C14 in these bones, then," I said.
"Yes, I did. But the C12 is now four million times more plentiful. About a quarter of the C14
is left. That means nearly enough, that two half-lives have passed." The doctor picked up one of the
brown toe bones. "It"s 12,000 years since this toe was broken. Perhaps the man was playing football
outside-with no boots on." |
| 1. The word "remains" in paragraph two means ______. |
A. things left by ancient people
B. dead bodies
C. newly-found ancient places
D. caves where ancient people lived |
| 2. Carbon 14 is a natural element (元素) ______. |
A. but it kills quickly
B. and we all have some in us
C. found only in bones
D. but it disappears after 5,600 years |
| 3. It is true that only ______. |
A. C14 has a half-life
B. old bones have a half-life
C. radioactive materials have a half-life
D. a living thing has a half-life |
本题所属标签:12十二1314151
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[优质解答]
.1+12+13+14×12+13+14+15-1+12+13+14+15×12+13+14=（）。
A.15
B.
12
C.1
D.0
本题所属标签:下列以下各式正确12十二A1213
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下列各式正确的是（ ）
| A．-＞-＞-
|
B．-＜-＜-
|
| C．-＜-＜-
|
D．-＜-＜-
|
|
本题所属标签:15141612十二131710
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15－4＋4＝ 4＋1－5＝ 14－14＋16＝ 1＋4＋15＝
1＋6＋12＝ 3－3＋8＝ 5＋13－12＝ 12－9＋14＝
14－5＋8＝ 17－5＋3＝ 3＋3＋5＝ 6－6＋7＝
16－5－7＝ 9＋10－2＝ 14－5＋11＝ 12－7＋14＝
本题所属标签:80kmhA12十二mm妹妹14
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80km/h<υmax≤120km／h混凝土枕地段正线及到发线，线路轨道静态几何尺寸临时补修容许偏差管理值中，水平、高低、直线轨向均为( )mm。
A、 12mm.14mm、12mm
B、 13mm.14mm、13mm
C、 12mm.14mm、14mm
D、 14mm.15mm、12mm
本题所属标签:比较对比大小结果正确12十二A12
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比较-，-，的大小，结果正确的是（ ）
| A．-＜-＜
|
B．-＜＜-
|
C．＜-＜-
|
D．-＜-＜
|
|
本题所属标签:四面体OABCaOBbOCcD中点AD向量
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如图，四面体O-ABC中，=，=，=D为BC的中点，E为AD的中点，则向量用向量，，表示为（ ）
|
本题所属标签:2212十二32714
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22÷1.2=（_________）÷12；3.27÷1.4=（_________）÷14
本题所属标签:阅读浏览理解计算12十二1314
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阅读理解：
计算(1+++)×(+++)-(1++++)×(++)时，若把(+++)与（++)分别各看着一个整体，再利用分配律进行运算，可以大大简化难度．过程如下：
解：设(++)为A，(+++)为B，
则原式=B（1+A）-A（1+B）=B+AB-A-AB=B-A=．请用上面方法计算：
①(1+++++)(+++++)-(1++++++)(++++)
②(1++…+)(+…+)-(1++…+)(+…+)． |
本题所属标签:1412十二
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=
A. 14 B. -14 C. 12 D. -12
本题所属标签:1412十二所以因数判断对错
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14比12大，所以14的因数比12的因数多．．（判断对错）
本题所属标签:文盲2008141612十二17245
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The United States is trying to improve an edueation system that produces millions of citizens who cannot read, write, or add—let alone finding their country on a map.
In his first State of Union message since taking office a year ago, President George Bush promised to wipe out illiteracy(文盲) in the next decade and declared that“by the year 2008, U.S students must be first in the world in math and science achievements. ” They have a long way to go. American students were placed 14th in a recent general science test conducted in 16 countries. In a separate survey of chemistry students, the United States came 12 out of 14. In a mathematics test, they were last. According to Bush, there are 17 million illiterates in this country of 245 million people. Other estimates put the number as high as 23 million. In percentage terms, that ranks the United States alongside Niearague and below Cuba. “This nation,”Bush said in his State of the Union address, “will not accept anything but excellent in education.” Bush, who has declared himself “Education president”, and senior officals of his administration are warning that the United States will be unable to compete in the world without an educated workforce.
How to increase educational standards is a matter of debate in a country whose schools have no uniform national curriculum and are subject to a confusing variety of state and local controls. Most experts think that the problem lies at the elementary and high school"levels rather than with universities-but even their graduates show huge gaps in general knowledge. Among the root causes most frequently mentioned in education debates is the low respect in which U.S. society holds teachers-in contrast to Japan and Germany. In Japan teaching is a profession of high prestige(威望) and high pay. In the United States teachers are near the bottom of the society.
5.By“the United States came 12 out of 14”(Para. 2), the author means .
A.the United States ranked 12th not 14th in the chemistry test
B.the United States ranked 12th in the chemistry test conducted by 14 countries
C.the United States progressed from 14th to 12th in the chemistry test
D.the United States ranked 12th in chemistry test and 14th in general science test
6.The cause of low educational level in America include the following EXCEPT that .
A.some problems exist in primary and secondary education
B.society keeps teachers in low respect
C.America pays more attention to economy instead of education
D.America has no uniform national courses
7.Which of the following statements can be inferred from the passage
A.President Bush carried out his promise made in his first State of Union message.
B.The education in Japan and Germany is in higher level.
C.According to Bush, the number of illiterates accounts for 9% of the total.
D.Teachers in the United States enjoy good treatment and great respect.
8.Which of the following is the right order of the least-first of the percent of illiterates
A.Germany, Cuba, Nicaragua. B.Germany, Nicaragua, Cuba.
C.Nicaragua, Japan, Cuba. D.Cuba, Japan, Nicaragua. |
本题所属标签:300减去1812十二所得除以14
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300减去18与12的积，所得的差除以14，商是多少？正确列式是（ ） ．
A.300-18×12÷14 B.(18×12-300)÷14 C.(300-18×12)÷14
本题所属标签:1412十二竖式中箭头所指一步表示
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如图，在14×12的竖式中，箭头所指的这一步表示的意思是？（ ）
A.10个14的和 B.12个14的和 C.1个14的和 D.2个14的和
本题所属标签:执行履行程序框图如果输入那么那末
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执行如图的程序框图，如果输入的N=4，那么输出的S=（ ）
| A．1+++
|
| B．1+++
|
| C．1++++
|
| D．1++++
|
|
本题所属标签:四面体OABCaOBbOCcD中点ADOE
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在四面体O-ABC中，=a，=b，=c，D为BC的中点，E为AD的中点，则可表示为（用a，b、c表示）．（ ）
| A．a+b+c |
B．a+b-c |
| C．a+b+c |
D．a-b+c |
|
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