问题 填空题

一个二位数加上9后,得到的和恰好是原二位数的个位数与十位数交换位置后的数的2倍,则原来的二位数是 ______.

答案

设原来的两位数为

.
ab
,个位数与十位数交换位置后的数为
.
ba
,由题意得,

10a+b+9=2(10b+a),

整理得19b-8a=9,①

由于a、b都是正整数,所以3|9,则3|a,3|b,

所以a、b可以为3、6、9中的任意两个,

代入①,经检验只有a=6,b=3符合要求,

所以原来的二位数是63.

故答案为:63.

阅读理解

The Internet has become part of teenagers’ life.

A news report on 3,375 students aged from 10 to 18 in seven Chinese cities found that 38 per cent of them believe they use the Internet often.

While most of them get useful information and use the Internet to help in their studies, some are not using it in a good way. Many are playing online games too much. A few even visit Web sites they should not look at. A middle school teacher from Beijing warns that bad things can happen if young people spend too much time on the Internet. She had a student who used to be good at school. But then he started visiting sex Web sites. He went mad, cheated a girl and was taken away by the police.

In order to help young people use the Internet in a good way, a textbook on good Internet behavior has started to be used in some Shanghai middle schools this term. The book uses real examples to teach students all about good ways of using the Internet. The book gives useful advice such as it's good to read news or find helpful information to study.

Some students also make online friends. But if you are meeting a friend offline, make sure your parents know. Teachers and parents all think the book is a very good idea. This teacher said the book will be a guide for teens using the Internet. She believes it will keep students away from bad sites. “Many students are using the Internet without guidance from their parents,” she said. “The book will teach students how to be a good person in the online world.”

小题1:The third paragraph mainly tells us that ________.

A.some students are not using the Internet correctly

B.all students in Beijing use the Internet to help their school work

C.a teacher in Beijing is worried about her students

D.some students visit sex Web sites小题2:The textbook mainly tells us ________.

A.why we should use the Internet

B.not to visit sex Web sites

C.how to use the Internet correctly

D.how to get help from others小题3:The writer advises the readers to ________.

A.let their parents know before visiting their online friends

B.not to make friends online

C.read the textbook carefully

D.only read news on the Internet小题4:From this passage we know that ________.

A.more and more students have given up visiting bad Web sites

B.schools and teachers begin to pay attention to students’ use of the Internet

C.no more homework will be given in Shanghai

D.less and less information can be found on line

单项选择题