Brain-Teaser Interview Questions Serve a Purpose Unusual questions allow hiring managers to see how potential employees think on their feet.

There was a lot of buzz a few months back, when news organizations began reporting on the odd -- sometimes very odd -- brain-teaser questions Google asks its interviewees. Odd: "Describe AdWords to a 7-year-old." Very odd: "How many haircuts do you think happen in America every year?"

But believe it or not, there's a method to Google's madness when it comes to lobbing unexpected and unusual questions at potential job candidates.

How Brain-teaser questions help recruiting.

While some of these riddles might feel, at first glance, like little more than a setup for failure (access a full list here), head scratchers like "How many piano tuners are there in the entire world?" serve an extremely important purpose when it comes to recruiting.

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Understanding how candidates "think," especially if they were faced with a sudden and unexpected workplace issue, is a vital piece of information for any HR professional. Are they good at calculations and estimating? Visualization and problem solving? Are they lacking in certain soft skills? Are they logical thinkers, or are they more apt to search for the "hardest" way out of a puzzle or business problem? (Still pondering the piano question above? Read on for the answer.)

Related: 15 Tips for Improving Your Skills Interviewing Job Candidates

A few puzzles to ponder

Many candidates today are well versed and well trained in interviewing techniques and most will walk into your boardroom with practiced, pat answers already locked and loaded. Brain teasers help throw them off their game a bit, just enough to allow you to see a different side of their personality.

Here are a few of my favorites, with the corresponding answers (or how to calculate them):

• "How many piano tuners are there in the entire world?" This teaser will help you determine whether a potential recruit is flexible enough to see "the big picture," and able to dissect a potential business problem from start to finish. Answer: This puzzle involves a lot of estimating, and finding the correct items to factor into the equation. Start with how many households have a piano, how often they are tuned, the average working hours of a piano tuner and the number of jobs a piano tuner carries out. Take the number of piano tunings that take place per year, divide by the number per year per piano tuner and you'll have a fairly good guesstimate.
• "An apple costs 40 cents, a banana costs 60 cents and a grapefruit costs 80 cents. How much does a pear cost?" This question makes a person really think outside the box, but the answer itself is very simple. Instead of complicated economics or price per unit, think vowels.
  Answer: If you charge 20 cents per vowel, the two-vowel word "apple" would cost 40 cents, three-vowel "banana" 60 cents, and four-vowel "grapefruit" 80 cents. Therefore, a pear would cost 40 cents.
• Describe the Internet to someone who woke up from a 30-year coma. I love this one because it provides the opportunity to get creative and have some fun -- something most nervous job applicants won't do, generally speaking.
  Answer: Of course, there is no real answer to this question, but you will be able to see who can think on their feet and tell a good story and who will choke -- useful information if the candidate will be in direct contact with clients.
• Why are manhole covers round? This question forces you to read between the lines and consider what's not being said, which is a valuable skill in business.
  Answer: The reason they're round is because a round manhole cover cannot fall through its opening, while a square one could if held diagonally—a dangerous possibility, needless to say. Puzzle solved, people safe.

I've saved the best for last -- I think I would have hired this guy on the spot:

• Say you are dead -- what do you think your eulogy would say about you?
  Answer: If you are dead, you cannot think about your eulogy.

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I hope you've had as much fun with these as I have. I would love for you to share some of your own unique brain-teaser questions -- and your favorite responses -- in the comments.