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标题: The highest prize and any rule? [打印本页]

作者: xyp 时间: 2013-1-29 06:54
标题: The highest prize and any rule?

Suppose a country only issued two types of coins to be used as currency: one 7 unit coin and one 11 unit coin. This would cause a dilemma since certain prices could

not be paid exactly, such as 13 units. What would be the highest price that could not be paid with any combination of the two coins? Could you find any rule to follow?^*

作者: findfun 时间: 2013-1-29 08:45
标题: 回复：The highest prize and any rule?

since 2*11-3*7=1, so if both sides have enough of each coins, you can pay any amount...

作者: fov22 时间: 2013-2-4 09:52
标题: 回复：The highest prize and any rule?

作者: xyp 时间: 2013-2-5 21:09
标题: [>:D<]

怎么算出来的？有什么规律可循吗？

作者: 冷眼看戏的Lili 时间: 2013-2-15 22:52
标题: 回复：The highest prize and any rule?

Let a and b be integers satisfying a>1 and b>1. Such a "highest prize" exists if and only if a and b are relatively prime. In this case, it is ab-a-b. For example, when a=11 and b=7, we get ab-a-b=59; when a=5 and b=9, we get ab-a-b=31.

本贴由[冷眼看戏的Lili]最后编辑于：2013-2-15 22:28:57

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