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问题 解答题

在学完“有理数的运算”后，实验中学七年级各班各选出5名学生组成一个代表队，在数学方老师的组织下进行一次知识竞赛。竞赛规则是：每队都分别给出50道题，答对一题得3分，不答或答错一题倒扣1分（1）如果（二）班代表队最后得分142分，那么（二）班代表队回答对了多少道题？ 

（2） （一）班代表队的最后得分能为145分吗？请简要说明理由。

答案

解：（1）设（二）班代表队答对了x道题，根据题意，列方程

 

解这个方程，得：

答：（二）班代表队答对了道题.

（2）答：不能.

设（二）班代表队答对了道题，根据题意列方程

 

解这个方程，得：

因为题目个数必须是自然数，即

不符合该题的实际情景，所以此题无解. 即（一）班代表队的最后得分不可能为145分.

单项选择题 B1型题

制备75％乙醇，即将75ml纯乙醇加入25ml蒸馏水，因此其百分浓度可计为（）。

A.体积-重量百分浓度

B.重量-重量百分浓度

C.体积-体积百分浓度

D.重量-体积百分浓度

E.以上均可
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单项选择题

What’s your earliest childhood memory Can you remember learning to walk Or talk The first time you heard thunder or watched a television program Adults seldom (1) events much earlier than the year or so before entering school, (2) children younger than three or four (3) retain any specific, personal experiences.

A variety of explanations have been (4) by psychologists for this "childhood amnesia". One argues that the hippo-campus; the region of the brain which is (5) for forming memories, does not mature until about the age of two. But the most popular theory (6) that, since adults don’t think like children, they cannot (7) childhood memories. Adults think in words, and their life memories are like stories or (8) one event follows (9) as in a novel or film. But when they search through their mental (10) for early childhood memories to add to this verbal life story, they don’t find any that fit the (11) . It’s like trying to find a Chinese word in an English dictionary.

Now psychologist Annette Simms of the New York State University offers a new (12) for childhood amnesia. She argues that there simply aren’t any early childhood memories to (13) . According to Dr. Simms, children need to learn to use someone else’s spoken description of their personal (14) in order to turn their own short-term, quickly forgotten (15) of them into long-term memories. In other (16) , children have to talk about their experiences and hear others talk about (17) --Mother talking about the afternoon (18) looking for seashells at the beach or Dad asking them about their day at Oceanz Park. Without this (19) reinforcement, says Dr. Simms, children cannot form (20) memories of their personal experiences.

Notes: childhood amnesia 儿童失忆症。

（20）（）

A.permanent

B.mental

C.spiritual

D.conscious
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