--- title: "How old is Ann?" url: https://daily.dev/posts/how-old-is-ann--lhglrdslo source_url: https://quuxplusone.github.io/blog/2026/07/29/how-old-is-ann type: article source: "Arthur O'Dwyer" published: 2026-07-29T23:07:38.805Z updated: 2026-07-30T16:09:02.602Z reading_time: 8 upvotes: 0 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # How old is Ann? **[Arthur O'Dwyer](https://daily.dev/sources/quuxplusone)** · 8 min read · 0 upvotes · 0 comments ## Summary A deep dive into the viral 1903 math puzzle 'How Old Is Ann?' — a word problem about the ages of two sisters that swept American newspapers and popular culture. The puzzle (Mary is 24, twice as old as Ann was when Mary was Ann's current age — how old is Ann?) spawned songs, plays, cartoons, and a flood of wrong answers from prominent citizens. The post collects contemporary newspaper quotes, humorous wrong solutions, parody poems, and cultural commentary showing how the puzzle became a short-lived national craze before fading away by late 1903. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Community take How the wider developer community reacted, aggregated from 1 discussion and 82 comments across hackernews (as of 2026-07-30). **TL;DR:** The community is largely engaged and collaborative, working through multiple approaches to solve the classic age puzzle (answer: Ann is 18), with lively debate about whether intuitive methods count as 'algebra' and what makes the problem tricky to parse. **Sentiment:** 60% positive · 30% mixed · 10% skeptical **The case for** - Rephrasing the problem (e.g., 'Ann's age is right in the middle of 12 and 24') makes it much easier to solve intuitively without formal algebra. - The problem is primarily a reading-comprehension challenge, not a math challenge — understanding the sentence structure is 90% of the work. - Multiple valid solution paths exist: algebraic, enumerative, and intuitive reasoning all arrive at Ann = 18. **The pushback** - The sentence structure comparing Mary's present age to Ann's past age is genuinely confusing and leads to common misreadings (e.g., getting 16 instead of 18). - Claiming the problem requires no algebra is disputed — introducing an unknown and writing an equation is algebra regardless of how informal it feels. - The problem is missing critical details about Ann's interstellar travel velocity, making 18 clearly the wrong answer (joke). **By community** - hackernews (positive): Commenters are enthusiastically collaborative, sharing multiple solution methods and debating the semantics of 'algebra' while converging on Ann = 18. **Hottest debate:** Whether solving the problem intuitively (without writing symbols) still counts as 'algebra,' with zephen and skipants/tempfile directly disagreeing. **Open questions** - Does solving a word problem 'in your head' without symbols constitute algebra or not? - Why does the common misreading produce 16, and is the original phrasing genuinely ambiguous? **Highlights** > > I can't see a way to do it without algebra. This is related to "When all you have is a hammer, everything looks like a nail." It's slightly different, because you've supercharged your hammer. Everything you ever understood about how to solve word problems has been subsumed into what your brain labels as "algebra." But look at it this way: 1) Did you use algebra to convert the problem to algebraic form? Probably not; algebra says nothing about word problems. 2) Once it was in algebraic form, did you need to repeatedly apply algebraic rules in order to reduce the problem, or could you glance at it and figure it out? You may also be hampered by your choice of variable, because you chose "X" to be an intermediate variable. If, instead, you choose "X" to be what you are searching for, Ann's current age, then the problem setup is: 24 - x = x - 12 Which many of us can solve in our heads without writing down, or even without consciously converting "Ann's current age" to "X". > — [zephen on hackernews · 2 comments](https://news.ycombinator.com/item?id=49110398) > Not the Flynn effect; just people having fun, and selection bias. I (the blogger) deliberately left out many boring responses, except for linking to the Evening World's letters page of 1903-11-11.[1] I filtered out scores of replies from schoolchildren walking through the algebra to get the correct answer, and dozens of (usually short) replies from people of various ages giving wrong answers with and without reasoning, some almost certainly joking, some almost certainly not. But that's what you should expect from a Letters to the Editor section on any given math meme! Our discourse hasn't changed that much over 120 years. See my other post,[2] linked at the bottom of the current one, on "What is 8÷2(2+2)?" — that's not as fair a question, but the discourse is pretty much the same in unfiltered Letters-to-the-Editor sections: "I think it's X. Well, I think it's Y." The whole point of this kind of meme is for the populace to perform disagreement about the answer! (See also: the Monty Hall problem; sports; comments sections.) [1] - https://www.loc.gov/resource/sn83030193/1903-11-11/ed-1/?sp=... [2] - https://quuxplusone.github.io/blog/2019/08/01/what-is-8-divi... > — [quuxplusone on hackernews](https://news.ycombinator.com/item?id=49110504) > This is more a test of reading comprehension than algebra. Figuring out what the questions is even trying to ask is like 90% of the question. > — [Jtarii on hackernews · 1 comments](https://news.ycombinator.com/item?id=49110492) > This may help people: > Mary is 24 years old. She is twice as old as Ann was (12) when Mary was as old (18) as Ann is now (18). How old is Ann? So 6 years ago, Mary was 18, and Ann was 12. Today, Mary is twice the age that Ann was (12 * 2) at the time that she (Mary) was 18, making her 24. What makes it confusing is that the sentence is comparing Mary’s present age with Ann’s past age (which I did not catch until mulling it over a bit). > — [sebmellen on hackernews](https://news.ycombinator.com/item?id=49111139) > Ah yes. The famous problem that is ambiguous because it ignores space travel! Let M_n := Mary's age now = 24, A_n := Ann's age now, and let M_p, A_p be the ages of Mary and Ann at a certain point in the past. We have that M_n = 24 = 2(A_p) from "Mary is 24 years old. She is twice as old as Ann was", immediately implying that A_p = 12. At the point in time p when M_p, A_p were the ages of Mary and Ann, respectively, we have that M_p = A_n from "when Mary was as old as Ann is now". Also, let x := | M_n - M_p | = | A_n - A_p | be the amount of time that has passed between the point p in time and now. Since M_n > M_p and A_n > A_p by construction, we can drop absolute values, yielding M_n = M_p + x, A_n = A_p + x. Substituting, we have M_p = 24 - x, and A_n = 12 + x, yielding x = 24 - M_p = A_n - 12, yielding A_n = 36 - M_p. But, since M_p = A_n, we can write 2(A_n) = 36 yielding A_n = 18. This problem, however, completely ignores the fact that Ann boarded an interstellar spaceship 6 years ago at a reasonable fraction of the speed of light c. To account for this missing detail, we need to use Lorentz factors. Since Ann was the one traveling in space, we have to adjust her current age by calculating A_p = A_n + x * sqrt(1 - (v/c)^2)), where v is Ann's velocity Given that the problem is missing the critical detail of how fast Ann is hurtling towards the outer boundary of the universe, we really can't calculate their age at all. Nonetheless, given the completely reasonable and plausible assumption that Ann has been traveling at 95% of the speed of light because spaceships totally can do that, Ann is obviously about 13.87 years old. So 18 years old is clearly the wrong answer. Note that the fact that Ann is not aging as much due to traveling at an enormous velocity does NOT change Mary's age. Mary remains exactly twice as old as Ann was at the given point in the past, so she's 24 and 6 years have passed from her perspective. Only Ann's age changes. Obviously. > — [simonreiff on hackernews](https://news.ycombinator.com/item?id=49110893) **Source threads** - [hackernews](https://news.ycombinator.com/item?id=49108971) · 38 points · 82 comments ## Similar posts on daily.dev - [Alice in Wonderland is mostly math jokes — Storica](https://daily.dev/posts/alice-in-wonderland-is-mostly-math-jokes-storica-lyjlmtwwv) · Hacker News · 0 upvotes · 0 comments --- [View this post on daily.dev](https://daily.dev/posts/how-old-is-ann--lhglrdslo)