题目内容
巧用“转折数”.将1到100中的合数排成一行,使得两个相邻的数都不互质,应该怎样排?
分析:可以先将因式中含2的合数排好,然后放6.再在6的后面放因式中含3合数,然后再在后面排15,接下来再在后面排因式中有5的合数.再放35就,然后再在后面排因式中含7合数.再放77,再在后面放因式中含11的合数.据此解答.
解答:解:根据以上分析排列如下:
4,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78,80,82,84,86,88,90,92,94,96,98,100,6,9,21,27,33,39,45,51,57,63,69,75,81,87,93,99,15,25,35,55,65,85,95,35,49,91,77,33.
4,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78,80,82,84,86,88,90,92,94,96,98,100,6,9,21,27,33,39,45,51,57,63,69,75,81,87,93,99,15,25,35,55,65,85,95,35,49,91,77,33.
点评:本题的关键是分类排列,然后再结合处找都含有两个相邻的因数的合数放在中间.
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