题面摘自 Henry E. Dudeney 公版文本；英文为古腾堡原文整理，中文为本站自译，提示、解答骨架和闲谈保留本站原创结构。
There is perhaps no class of puzzle over which people so frequently blunder as that which involves what is called the theory of probabilities. I will give two simple examples of the sort of puzzle I mean. They are really quite easy, and yet many persons are tripped up by them. A friend recently produced five pennies and said to me: "In throwing these five pennies at the same time, what are the chances that at least four of the coins will turn up either all heads or all tails?" His own solution was quite wrong, but the correct answer ought not to be hard to discover. Another person got a wrong answer to the following little puzzle which I heard him propound: "A man placed three sovereigns and one shilling in a bag. How much should be paid for permission to draw one coin from it?" It is, of course, understood that you are as likely to draw any one of the four coins as another.
也许没有一类谜题比涉及所谓概率论的谜题更容易让人犯错。我将举两个简单的例子来说明我所说的谜题。它们确实很简单，但很多人却被它们绊倒了。最近，一位朋友拿出了五枚硬币，对我说：“同时扔这五枚硬币，其中至少有四枚硬币全部正面或反面的几率有多大？”他自己的解决方案是相当错误的，但正确答案应该不难发现。另一个人对我听到他提出的以下小谜题给出了错误的答案：“一个人将三枚主权硬币和一先令放入一个袋子中。要获得从袋子中提取一枚硬币的许可，需要支付多少钱？”当然，您可以理解，您抽出四枚硬币中任何一枚的可能性与抽出另一枚硬币的可能性相同。
提示 1
先把图画成可量的对象，标出边、格点或切割线。
提示 2
找面积、长度、对称轴或不变量，不急着剪。
提示 3
若是重排题，检查每一块在移动前后是否保持形状和面积。
完整解答
把题目先放到方格纸上。若四块面积相等，每块面积是总面积的四分之一；“轮廓相同”要求两道切割线在旋转或翻折后能互相对应。解题主线是先画出中心对称或四分旋转的候选，再用方格计数核对每块面积。
Dudeney 的趣题常把难点藏在“看起来可以试”的地方。别急着猜答案；先把图、表或状态画出来，再问哪些限制一直没有变。这也是它和 Carroll 逻辑题互补的地方：一个拆句子，一个拆结构。