If 500 is the mutiple of 100 that is closest to x and 400 is the multiple of 100 that is closest to y,which multiple of 100 is closest to x+y? (1)x小于500 (2)y小于400
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ken@boost.org.cn
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调查1200人对A B C 的喜好,喜欢A的40%,喜欢B的58%,喜欢C的40%,同时喜欢AB的30%,求喜欢C但不喜欢A B的人
题目:A Printer numbered consecutively the pages of a book, beginning with 1 on the first page. In numbering the pages, he printed a total of 189 digits. How many pages are there in the book?
问题:看了中文翻译并听了管老师的讲解,我都没弄明白这个题目的解题思路。的别是对“a total of 189 digits”的处理。
题目:If n is a prime number greater than 3, what is the remainder when n的平方is divided by 12?
问题:当管老师解题时,他出了3个方程式,分别是:
1) n=3A+1, n的平方=9A(square)+6A+1
2) n=3A+2, n的平方=9A(square)+12A+4
3) n=2A+1, n的平方=4A(square)+4A+1
我不明白的点是:这3个方程式是怎么推到或者是一看到题目就这么设出来的?