Technical interviews are an attempt by a hiring team to ask the correct questions of a candidate to determine if they would be a good technical fit for the open position.
These questions can sometimes uncover missing segments of knowledge that might identify opportunities for the candidate, or even disqualify the candidate for the open position. That is good information to know before you initiate the hiring process, but it can also help identify specific talents or abilities in a candidate that are above and beyond the minimum knowledge expected.
One of the obvious pitfalls of the technical interview is if the questioning turns into more of a trivia contest than a verification of expected knowledge.
One way to determine if a candidate knows how to solve a problem is to give them a problem and ask them to solve that problem during the interview. Sometimes the problem can be a specific technical issue, or a theoretical problem that is just to see if they can determine a simple solution using just the facts presented.
I have asked a simple question to candidates in the past that doesn’t really apply to the job opening they are applying for, but does provide insight into how they identify the issue, think through the possible answers, and provide them an opportunity to present their ideas.
Why is a manhole cover round?
You may never have thought of this question before, but why is a manhole cover round? You want the candidate to consider the possibilities and try to provide possible reasons for this design choice. It has nothing to do with the position they have applied for, but it will give a hiring manager an idea of how this person will respond to a problem that seems to come out of left field.
Do they think though the question or just respond with “I don’t know.” and quit? Have them speak about what they think about the question. Do they have an opinion about why they aren’t square, hexagon, or even oval in shape? Have they seen a manhole or know what they are used for in everyday life? Why do they think some manholes covers are not round?
Hopefully they can speak to possible reasons, which gives you the opportunity to ask how they would find a suitable response. If they just want to Google the answer, maybe ask them what else you might do to get a suitable answer if there isn’t a consensus on Google.
The possible correct answers are:
- Manhole covers are round because it is the best shape to resist the compression of the surrounding soil.
- Round manhole covers are easier to manufacture, move, and place than square or rectangular ones. The heavy covers can be easily rolled into position.
- Manhole cover the size to fit the opening cannot fall through the circular opening, unlike other shapes. No one wants a 100-pound manhole cover dropping onto their head.
- The cover doesn’t have to be aligned in any specific angle to be placed back onto the exposed manhole. Other shapes would require precise alignment.
Years ago, there was a candidate that guessed the covers are round because the men accessing the opening are also round. While this is funny, I don’t think that was a design consideration.
I hate interviews that turn into trivia contests, so I’d much rather be asked a tough question that allows me to show my ability to use my brain to find solutions instead of just demonstrating my ability to memorize technical trivia that anyone could easily look up.
(1) Why Are Manhole Covers Round? | Mental Floss. https://www.mentalfloss.com/article/60929/why-are-manhole-covers-round.
(2) Why are manhole covers round? | Live Science. https://www.livescience.com/32441-why-are-manhole-covers-round.html.
(3) Why Are Manhole Covers Round? – ScienceABC. https://www.scienceabc.com/eyeopeners/why-manhole-covers-circular-not-triangular-square-rectangular.html.
(4) The Surprisingly Technical Reason That Manhole Covers Are Round. https://www.envirodesignproducts.com/blogs/news/the-surprisingly-technical-reason-that-manhole-covers-are-round.