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。
The proprietor of a small London café has given me some interesting figures. He says that the ladies who come alone to his place for refreshment spend each on an average eighteenpence, that the unaccompanied men spend half a crown each, and that when a gentleman brings in a lady he spends half a guinea. On New Year's Eve he supplied suppers to twenty-five persons, and took five pounds in all. Now, assuming his averages to have held good in every case, how was his company made up on that occasion? Of course, only single gentlemen, single ladies, and pairs (a lady and gentleman) can be supposed to have been present, as we are not considering larger parties.
伦敦一家小咖啡馆的老板给了我一些有趣的数据。他说，独自到他家喝点心的女士们平均每人花费十八便士，无人陪伴的男士每人花费半克朗，而当一位绅士带一位女士进来时，他花费半几尼。除夕夜，他为二十五人提供晚餐，总共拿了五英镑。现在，假设他的平均值在每种情况下都保持良好，那么当时他的公司是如何构成的呢？当然，只有单身男士、单身女士和双人(一位女士和一位男士)可以出席，因为我们不考虑大型聚会。
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。