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Comment by cableshaft | Hacker News Reader

I was expecting something a little different, where they passed on him because he didn't give the 'right' answer (what the interviewer had preconceived and/or looked up online).

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100%. The answer wouldn't be "join our marketing team", it would be "you aren't a culture fit".

Ye, they really don't like people who think at marketing departments.

You know how police have to take an IQ test and get denied the job if they score too high?

Like that, but for tech interviews.

I think it's a rare practice right?

"... the theory that those who scored too high could get bored with police work and leave soon after undergoing costly training."

I must be a genius. I'm sooo bored at my software dev job.

https://abcnews.go.com/US/court-oks-barring-high-iqs-cops/st...

or it's time to change job :)

I feel like most jobs get boring in a year or less. Usually it's due to the bureaucracy and not having any input into the business systems that were implement in the tech.

Bored like Peter Gibbons?

https://www.youtube.com/watch?v=j_1lIFRdnhA

Maybe you need a promotion.

https://www.youtube.com/watch?v=af8DVIZ5LX4

There are a lot of good points in there

> police have to take an IQ test and get denied the job if they score too high

Pilots as well, apparently.

Well yea, that expectation was produced purposefully in order to be subverted for the actual punchline.

Well, that _is_ the conceit here. The ‘right’ answer is that all manhole covers are round because a round cover can’t fall into the hole.

I'm fairly certain a square manhole cover with a sufficient perimeter would still have no chance of falling into a hole, depending on the diameter of said hole.

If you provide a sufficient lip on the hole such that the minimum side is larger than any of the four diagonals it would work.

Right, but this makes the area of the cover twice the area of the hole, and the cover twice as heavy as it would need to be if it were round. As Feynman pointed out, even round covers are already pretty heavy—I injured my wrist (ligaments?) from the tension of lifting one in my teens.

However, if this were the only consideration, you could get a wider-diameter manhole with a smaller cover by making it in the form of an equilateral triangle, as evidently Nashua, NH, does: https://en.wikipedia.org/wiki/Manhole_cover#Other. Indeed, you don't need to stop there; if you curve the sides of the triangle in toward the center, you can get a manhole with an even smaller surface area for a given diameter, although at some point the extra "diameter" will be too curved to be useful.

Indeed, though to do it this way would be very wasteful of resources as the ratio of the manhole size to the size of the cover wouldn't be maximized. The cover would be needlessly covering a lip whose large size only exists because of the poor choice of shape.

It explains in the joke how it's possible to fit a square cover into a slightly smaller square hole. The easiest way is to position the cover vertically and across the diagonal. The lip that the square cover rests on would have to be impractically large to fully prevent the cover from fitting into the hole.

If we're talking square cover, round hole, no cover big enough to cover the hole could fall in.

If I know anything about capitalism, the primary reason manhole covers are round is because that's the most cost-efficient shape for the job.

This is almost certainly the answer. They're round to fit the cylindrical holes they're covering, and those holes are round because they're made with drills, and they're made with drills because that's a lot faster and cheaper than digging.

Tunnels are round because a round tube on the inside is stronger against compression than an equivalent square tube is. They are like vaults.

Many manholes are in fact squared. So the premise itself is wrong.

This is pointed out in the first two words of the "Feynman" answer ("They're not.")

Let's just say there are many questions that people ask in interviews where they have a scientific sounding answer that is simple and wrong (when considered in full context).

it's not your job to consider it in full context and give the globally true answer (as feynmann attempted here). it's your job to be cleverer than the interview, perceive what they want to hear, and tell it back to them in a way that maximizes the score they give you on the interview.

The reason you do that is it directly impacts the size of the job offer they give you if you answer questions exactly the way you want to hear. It's eminently rational, and a form of social engineering. Once you're hired you can advocate for change from within *

* I tried to get google to change many of it's stupidest hiring practices for years but it was tilting at a windmill

This has nothing to do with full context and some obscure scientific fact. The squared manholes are super common. Many of them are squared and I probably stepped over some squared on my way to interview.

It is like asking why milk is sold always in yellow box. The question makes no sense, because milk boxes can have any color.

Manhole covers are round so you can move them by rolling them around. Duh

But a triangle works for this, too.

Pretty sure I can toss a triangular cover into a triangular hole. You might be thinking of a Reuleaux triangle (which is not a triangle, narrowly conceived.)

https://en.wikipedia.org/wiki/Reuleaux_triangle

Yes, you're right, it's actually a curved triangle; or any curved shape with a constant width. The key aspect is that it has to have a constant width.

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