试题与答案

一个两位数中间插入一个一位数（包括0），就变成一个三位数，例如72插入6后成了7

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题型：解答题

题目：

一个两位数中间插入一个一位数（包括0），就变成一个三位数，例如72插入6后成了762．有些两位数中间插入某个一位数后变成的三位数，是原来两位数的9倍，这样的两位数有几个？分别是多少？

答案：

设原两位数为10a+b，中间插入后为100a+10c+b，9（10a+b）=100a+10c+b，5a-4b+5c，a+c=

4
5
b，

因为a，b，c都是非负整数，

所以b是5的倍数，

当b=5时，a+c=4，a=1，2，3，4，c=3，2，1，0，

分别是15，25，35，45共4个．

考点：写代数式
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题型：阅读理解

阅读理解

     British scientists may have discovered the reason why red wine appears to protect the heart. They

say natural chemicals found in red wine appear to protect against blocked blood vessels(血管). The

chemical substances are called poly-phenols(多酚). They come from the outer covering of grapes. They

are not present in other alcoholic drinks.

     Researchers say their discovery explains why many people in southern Europe can eat fatty foods and

still have a low risk of heart disease. People in France, for example, have lower rates of heart disease

than Americans do. Yet the traditional French diet includes butter, cheese and other foods high in

cholesterol(胆固醇). This led the British scientists to examine another important part of the French

diet - red wine. Several earlier studies have suggested that people who drink proper amounts of alcohol

may reduce their risk of heart disease.

     The British team experimented with cells from the blood vessels of cows. The scientists studied the

effects of twenty-three kinds of red wine on the cow cells. They found that poly-phenols from all of the

red wines stopped production of a protein called endothelin(内皮素). This protein causes blood vessels

to become smaller. Scientists believe endothelin is linked to hardening of the blood vessels, which is a

cause of heart disease.

    The scientists found that the decrease in endothelin levels was linked to the amount of poly-phenols in

the wines. The British team performed similar experiments with two other kinds of wine, white and rose.

These wines contain little or no poly-phenols because the grape skins are removed before the wine is

made. White and rose wines had no effect on endothelin levels.

     The scientists also studied the effect of non-alcoholic juice made from red grapes. They found that

grape juice slowed the production of endothelin, but was much less effective than the red wines.

1. So far as grapes are concerned,           is more effective on reducing the risk of heart disease.

A. the outer part of grapes

B. the inner part of grapes

C. the seeds of grapes

D. the juice in grapes

2. What made the British scientists study another important part of the French diet?

A. Traditional French diet.

B. Lower risk of heart disease of the French.

C. The reason why people drink wine.

D. Poly-phenols not existing in other things.

3. From this passage, we may know people's health is linked to           .

A. diet habits  

B. their genes

C. their education

D. living surroundings

4. What's the best title for this passage?

A. A Healthy Diet

B. Protecting Your Heart

C. Red Wine and Health

D. A Study on Health
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