[glofish]

I believe that the author misremembers the common solution for the first question

> 3 hens lay 3 eggs in 3 days. How many eggs do 12 hens give in 12 days?

> [...] When we got to it, everybody shouted "Three!"

I don't see why the "common" wrong answer would be 3. Why would anybody think that? The problem looks like this 3, 3 -> 3

When we see the 12 and 12 the intuitive, common, wrong answer should be 12 eggs.

That's what makes sense IMHO.

[photochemsyn]

How to annoy the teacher:

> "Ovulation (release of the yolk from the ovary) occurs every 24 – 26 hours regardless of fertilization (so a rooster is not needed). A hen ovulates a new yolk after the previous egg was laid. It takes 26 hours for an egg to fully form (white and shell added), so a hen will lay an egg later and later each day. Eventually the hen will lay too late in a day for ovulation to be signaled. She will then skip a day or more before laying another egg." (UWisconsin Livestock)

So, the 3 hens must have been at the least productive point in their egg-laying cycle over the initial three-day time period... Now if we have the two-hour daily offset, over 12 days, ummm, maybe two or three days skipped per hen? So, ah, 108-120 eggs is what the farmer could expect from the 12 hens?

[dvh]

I remember a story where school teacher was showing plastic animals and asking kids what it was. At some point all kids wrote "cow" except for one farm boy who wrote "goat". Turns out the plastic cow had wrong number of udders. Cows have four, goats have two.

[mlajtos]

Once I saw 5-armed snowflake as an icon on weather forecast in TV.

[dusted]

You meant teats, they both have one udder, but otherwise right :)

[mlajtos]

This is gold!

[moondrek]

I read it as the students being familiar with a similar "trick" question and erroneously pattern matching on that.

Another similar riddle goes like:

"If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?"

The correct answer there being "5 minutes", and the intuitive wrong answer being "100" as per your post.

That would make sense as to why the teacher also expected "3", since they should be familiar with the existence of their non-intuitive questions, even if they misremember the specific non-intuition.

[Cthulhu_]

Or as to why adding more people to a late project makes it later: 1 woman takes 9 months to grow a baby, how long does it take 9 women to grow a baby?

[mlajtos]

Of course it was "Twelve!". Thank you for bringing this up. It is fixed now.

[thechao]

I took me surprisingly long to convince myself the author was correct: the answer is 48 because there's 4x as many hens and 4x as many days: 3 x 4 x 4 = 48. The "wrong" way to solve this problem is to compute hen-laying in terms of hen-egg-days, and then scaling.

[jaclaz]

>The "wrong" way to solve this problem is to compute hen-laying in terms of hen-egg-days, and then scaling.

I am not sure to understand what you mean by "wrong" way, I got the right result through a different reasoning that seems to me based on hen-egg-days.

It takes 3 days for 3 hens to make 3 eggs.

The 3 days time are "fixed", i.e. it takes 3 days for each hen to make its own egg.

The egg production rate is 1/3 egg per day per hen.

So I have 12 hens x 12 days x 1/3 = 144 x 1/3 = 48

[c22]

I dunno, I immediately noted that 12 hens must lay 12 eggs in 3 days (it takes 3 days for a hen to lay an egg). Then I just asked myself how many 3-days are in 12-days--okay, 12 [eggs] * 4 [3-day egg periods] = 48...

I didn't need to resort to pen and paper, but I'm also not in primary school.

[jimmaswell]

I always skip straight to dimensional analysis for such a thing.

3 eggs / 3 chickens / 3 days * 12 chickens * 12 days cancels out to 48 eggs

[jkubicek]

There are a lot of right ways to solve this problem, but this is clearly the most fun way.

[hgsgm]

That's because it's output/input = eggs/(hen*day), not eggs/(hen/day), which is clear from meaning and logic if you aren't a GPT 2 LLM

[mlajtos]

There is a visual illustration in the article. I thought it might be useful for understating why it's 48.

[ouid]

He misremebered the third task as well, since his solution to it, as stated, is wrong. If you aren't given that every card has a number on one side and a color on the other, then you need to check everything which does not satisfy the consequent.

[mlajtos]

I added "We have cards with a number and color on each face." to the task statement. Hope this makes rules clearer as I could not phrase it better.

[ouid]

The rules were clear before, what has changed is that they are now different rules. You were just wrong before.

You've still got a problem though, now when you ask the reader to verify the rule, you have to explicitly state that they're not trying to verify the first rule.

[mlajtos]

Oh shit, you are right. Added a completely explicit statement under the problem question. In both situations.

Thank you for pointing this out.

[menzoic]

the article says everyone shouted 12 not Three

[forbiddenlake]

It said 3 originally.

https://news.ycombinator.com/item?id=35688034