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问题 填空题

徐工集团某机械制造厂制造某种产品，原来每件产品的成本是100元，由于提高生产技术，所以连续两次降低成本，两次降低后的成本是81元．则平均每次降低成本的百分率是              ．

答案

10％

题目分析：设平均每次降价的百分数是x，根据降低后的价格=降低前的价格×（1-降低率），则第一次降低后的价格是，那么第二次降价后的价格是，即可列出方程求解．

设平均每次降价的百分数是x，由题意得

解得或（不合题意，舍去）

则平均每次降价的百分数是10%.

点评：解答本题的关键在于分析降价后的价格，要注意降价的基础，另外还要注意解的取舍．

多项选择题

新生儿生理性黄疸的主要原因是（）

A.胆红素生成过多

B.Y、Z蛋白不足

C.肝酶系统发育不完善

D.肠内β葡萄糖醛酸苷酶活性较高

E.血清白蛋白含量低
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单项选择题

For many people today, reading is no longer relaxation. To keep up their work they must read letters, reports, trade publications, interoffice communications, not to mention newspapers and magazines: a never ending flood of words. In (1) a job or advancing in one, the ability to read and comprehend (2) can mean the difference between success and failure. Yet the unfortunate fact is that most of us are (3) readers. Most of us develop poor reading (4) at an early age, and never get over them. The main deficiency (5) in the actual stuff of language itself—words. Taken individually, words have (6) meaning until they are strung together into phrases, sentences and paragraphs. (7) , however, the untrained reader does not read groups of words. He laboriously reads one word at a time, often regressing to (8) words or passages. Regression, the tendency to look back over (9) you have just read, is a common bad habit in reading. Another habit which (10) down the speed of reading is vocalization—sounding each word either orally or mentally as (11) reads.
To overcome these bad habits, some reading clinics use a device called an (12) , which moves a bar(or curtain) down the page at a predetermined speed. The bar is set at a slightly faster rate (13) the reader finds comfortable, in order to "stretch" him. The accelerator forces the reader to read fast, (14) word by word reading, regression and subvocalization practically impossible. At first (15) is sacrificed for speed. But when you learn to read ideas and concepts, you will not only read faster, (16) your comprehension will improve. Many people have found (17) reading skill drastically improved after some training. (18) Charlie Au, a business manager, for instance. His reading rate was a reasonably good 172words a minute (19) the training; now it is an excellent 1,378 words a minute. He is delighted that how he can (20) a lot more reading material in a short period of time.

A．Fortunately
B．In fact
C．Logically
D．Unfortunately
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