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标题: 种树 [打印本页]

作者: fzy 时间: 2005-4-4 18:38
标题: 种树

1. 10棵树种成5行，每行4棵，怎么种？ (Difficulty: +)

2. 11棵树种成6行，每行4棵，怎么种？ (Difficulty: ++)

3. 12棵树种成7行，每行4棵，怎么种？ (Difficulty: ++)

4. 13棵树种成9行，每行4棵，怎么种？ (Difficulty: +++)

作者: 新用户 时间: 2005-4-4 22:21
标题: 挑个简单的，我来回答第一题

就是在五角星焦点处种树，5条线就是5行，每行4颗。

作者: yma16 时间: 2005-4-4 22:56
标题: 回复：11棵树种成6行，每行4棵

a a a a
a a a a
a a a a
a a a

作者: sean9991 时间: 2005-4-4 23:17
标题: 2 and 3

2 and 3

作者: sean9991 时间: 2005-4-4 23:19
标题: answer for 2 and 3（图）

作者: sean9991 时间: 2005-4-4 23:20
标题: isn't that 15 trees?

isn't that 15 trees?

作者: 怀疑 时间: 2005-4-5 02:20
标题: I got an answer for No. 4

I got an answer for No. 4

作者: 怀疑 时间: 2005-4-5 02:33
标题: 回复：I got an answer for No. 4（图）

作者: 怀疑 时间: 2005-4-5 02:38
标题: 回复：回复：I got an answer for No. 4（图）

First draw four lines.

作者: sean9991 时间: 2005-4-5 07:13
标题: answer for 4（图）

作者: 欢歌角度 时间: 2005-4-5 07:20
标题: 和前面的是一样的

和前面的是一样的

作者: fzy 时间: 2005-4-5 18:30
标题: Well done

The two answers for No. 4 (as well as my own answer) are structually the same. I solved it this way: Start with one line and two points on the line. Draw three other lines from each point. These six lines intersect and form a " 田字". Adjust the "田字" so that its two diagonals intersect the original line.

As far as I know, 9 is the best known result for 13 trees. The exact upper bound is still unknown, that is, no one proved it is not possible to have 10 rows, and no one did it either.

作者: yma16 时间: 2005-4-6 00:29
标题: 回复：you are right.

回复：you are right.

作者: fzy 时间: 2005-4-6 19:29
标题: ranking

Recently problem 4 appeared at WXC, with a ranking similar to the following:

6 rows : High School
7 rows : Bachelor
8 rows : Master
9 rows : Ph.D

Nice to see some Ph.D's here . There is only one Master and some Bachelors at WXC.

作者: 怀疑1 时间: 2005-4-6 21:35
标题: I am also in WXC but did not see this problem

I am also in WXC but did not see this problem

作者: fzy 时间: 2005-4-6 21:43
标题: 回复：I am also in WXC but did not see this problem

http://web.wenxuecity.com/BBSView.php?SubID=netiq&MsgID=30918

作者: 怀疑1 时间: 2005-4-6 22:36
标题: 回复：回复：I am also in WXC but did not see this proble

You are right. I did not notice this problem. It seems that only two people at WXC tried, and these two guys are not among the best there.

作者: fzy 时间: 2005-4-6 23:42
标题: I know. They probably didn't notice it either.

I know. They probably didn't notice it either.

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