That odd specificity to me was the big red flag for me that it was a total bullshit answer to BEGIN with.
“How would I get that with no calculator, and no access to a formula, unless … oh, yeah. Ok.”
Anger and flip dismissal of something perceived to be irrelevant is one of those strategies that doesn’t work well when you’re knee deep in troubleshooting problems in code, networking, whatever.
I agree that it’s not awesome form to deploy these little bombs in an interview, and I certainly wouldn’t- but seeing how somebody’s behavior when faced with a seemingly irritating customer could be a coarse-grained weedout.
If a prospect flipped the table and said “Fuck this, I don’t need the job” and walked out, fine, maybe we weren’t meant for each other.
If someone can’t control their behaviour when confronted with something they don’t like then they might be a bad hire. But if someone asked me that question in an interview and later I looked up the actual formulas involved I would avoid taking the job (if I could) because I’d think hiring manager was an idiot.
I’ve come to the point in my career and my life that I now walk away from job prospects that force me to complete some BS “skills” test or work exercise prior to having an actual face-to-face interview. If they’re going to use this as a means to weed out candidates then let me save you the trouble.
I feel like Crash Davis in Bull Durham: “After 12 years in the minor leagues, I don’t try out.”
I do believe that if it were stated as in the interview question and not as it is here, I would have spotted it, but my tendency would be to work through the first part of the question first.
Out of uni and making the rounds for a position someplace, and one interviewer (some analysis group head) asked me to derive F=ma. Luckily, our high school aero class drummed that one into us long before. Go, Tech!
I approximated the curve of the half cable by a straight line. Then with the help of Mr. Pythagoras, I got a figure of 52.9m, an error of 16.5%. That should be good enough for any job interview.
Catenary: the mathematical equation that answers the question, “How’s it hanging?”.
I will say, though, that a simple triangle would be an ok-ish first approximation. An elipise would be better, and a parabola better still, I think. Still wrong, but now we’re getting into the realm of “well actually the Earth is an oblate spheroid.” Particularly since we have one decimal place to play with (aaand I choose the km as my unit of measure, so 1dp gives me 100m of slop )
I will repeat here my family’s favourite riddle: if it takes a week to run a fortnight, how many apples in a pound of pears? [edit: there is a correct answer…]
The one time I was confronted with a question like that, “I would look up the correct answer” was, in fact, the right answer to the question. (Though you have to specify how you would do the research)
It really comes down to what the questioner values. Which could be humility and honesty.
Is this question directly relevant to the job? Because if it isn’t then I have dyscalculia and we are in a country that still takes disability discrimination somewhat seriously, at least for the moment.
Actually, forget the job. I will be talking to your legal team soon.
It would be better phrased as “Each end of an 80 meter cable is attached to the top of a 50m pole. What is the distance between the ends of the cable if the centre of the cable is 10m off the ground?”
There are no lies in that version, unlike the original which specifies two poles where there can only be one.
(aaand I choose the km as my unit of measure, so 1dp gives me 100m of slop 
)