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。
Tommy: "How old are you, mamma?" Mamma: "Let me think, Tommy. Well, our three ages add up to exactly seventy years." Tommy: "That's a lot, isn't it? And how old are you, papa?" Papa: "Just six times as old as you, my son." Tommy: "Shall I ever be half as old as you, papa?" Papa: "Yes, Tommy; and when that happens our three ages will add up to exactly twice as much as to-day." Tommy: "And supposing I was born before you, papa; and supposing mamma had forgot all about it, and hadn't been at home when I came; and supposing——" Mamma: "Supposing, Tommy, we talk about bed. Come along, darling. You'll have a headache." Now, if Tommy had been some years older he might have calculated the exact ages of his parents from the information they had given him. Can you find out the exact age of mamma?
汤米：“妈妈，你多大了？”妈妈：“汤米，让我想想。好吧，我们三个年龄加起来正好是七十岁。”汤米：“很多了，不是吗？爸爸，你多大了？”爸爸：“孩子，只有你六倍大。”汤米：“爸爸，我的年龄可以只有你的一半吗？”爸爸：“是的，汤米；当这种情况发生时，我们的三个年龄加起来将是今天的两倍。”汤米：“爸爸，假设我出生在你之前；假设我来的时候妈妈不在家；假设——” 妈妈：“假设，汤米，我们谈论床上的事。来吧，亲爱的。你会头痛的。”现在，如果汤米再大一些，他可能就能根据父母提供给他的信息计算出他们的确切年龄。你能查出妈妈的具体年龄吗？
提示 1
先说出现象：哪些量会变，哪些约束不会变。
提示 2
找守恒量、相似关系、平衡条件或不变量，不急着代公式。
提示 3
把物理图景或谜题结构翻成一个最小方程组，再处理边界情况。
完整解答
解题主线是先把 Dudeney 谜题 10 的条件整理成一个稳定模型，再选择最少的变量。第一步确认约束，第二步写出关键关系，第三步检查特殊情形。这里给的是原创解法骨架；若要核对原始题面，请回到公版来源。
这类题最怕一上来套公式。先把图景或语言条件说清楚，答案通常会少绕很多路。