Tech companies are notorious for asking impossible interview questions meant to stump job candidates and demonstrate how they think on their feet. Google abandoned these types of questions several years ago, and executives later admitted that even they could not solve them, but several companies continue to use them as part of the interview process.

These types of questions can either hurt or harm an interview, said Jen Teague, a small business staffing and onboarding coach. “When the interviewer has good grasp of the hiring procedures and what to look for, these can be very insightful as to how a candidate thinks,” Teague said. “However, when they are added for no purposeful reason, they will turn away good candidates. These are really good for STEM-related fields but not usually as appropriate for other industries.”

Max Page, the founder of CouponHippo, interviewed at Google a few years ago. He said he was asked questions including “Estimate how many Android handsets will be activated in the US this year,” and “Estimate how many planes are flying over the United States right now.”

“They want to hear you think out loud the whole time,” Page said. “I don’t think it should be a hire, no-hire question. But I do think you get some value out of hearing people think out loud. The final number isn’t very important. Just the journey the candidate takes to get the final number.”

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Objective, a design and development studio, does not use brainteaser questions during interviews–instead, interviewers give applicants a small project to complete prior to the interview that mirrors the type of problem solving expertise they are seeking, said CEO Brett Derricott. “We value the self-motivated, self-directed problem solver,” Derricott said. “We believe the brainteaser-type questions may also eliminate intelligent, talented applicants who problem solve less effectively during an interview with the pressure of one or more interviewers watching.”

Brainteaser questions can reveal a candidate who is logical, mathematically-minded, and quick on their feet, said Lauren McAdams, a career advisor and hiring manager at However, they can also be distracting.

“Some hiring managers will be overly impressed by someone who quickly answers a brainteaser, but then neglect to put the same kind of emphasis on questions of integrity, personability, and culture-fit,” McAdams said. “Besides, some people just think differently, and even individuals are prone to respond differently on different days.”

Here are 10 brainteaser interview questions for you to consider adding to your interview process.

1. If I say there are a billion and ninety nine stars in the sky, how would you prove me wrong?

Social platform Grin usually asks this or another brainteaser at the last stage of the interview process, said director of marketing Pratik Shah. “We’re always looking for team players, positive people, someone who can lighten up the chaotic start-up work environ,” Shah said. “We’re not looking at the final answers; most of the times we don’t know them ourselves. We’re looking at the ‘fun factor’ in tackling those questions. We do want to see how the candidates conduct themselves in uncomfortable situations. What’s their approach? And what’s the style of their answer? This interview technique does help us uncover gems.”

2. A Boeing 747 is full of jelly beans, how do you empty it?

Experts Exchange, an online community of community of more than 500,000 IT professionals, recently polled its community of IT professionals on the hardest interview question they had ever been asked. This question was submitted by a senior analyst at Computer Science Corporation.

3. How many gas stations are there in the county?

Bianca Jackson, a career happiness expert, was asked this question for a business analyst job. “I took my best guess based off the number of major intersections,” Jackson said. “Initially, the question seemed unrelated to the position. But I soon realized that interviewers use the technique to assess candidate’s critical thinking ability.”

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4. How many pennies would you have to stack to reach the height of the Empire State Building?

This question was submitted no Experts Exchange by a chemist at EFI.

5. Give me at least three things, other than writing, that you can use a pencil for?

Human resource specialist Ashley Lounds Brooks often stumps interviewees with this question. “I want to know that the people I am hiring can think outside of the box and offer more than just that one thing,” she said.

6. How would you direct someone to make an omelette?

A data analyst from PETCO submitted this brainteaser to Experts Exchange.

7. Are you the smartest person you know?

Tom Borghesi, COO at Open Systems Technologies, said he likes to catch job candidates off-guard at the end of an interview with this question. “Often times the interviewee will answer no out of modesty,” he said. “If they do, then I ask who is the smartest person they know, and I try to hire him or her.”

“I think it’s important to see how someone handles pressure,” he said. “If they keep their cool and are also able to give an honest and insightful answer I’m always impressed. If they have a good sense of humor about being put on the spot then they are generally easy to integrate as a member of the team.”

8. Plan the evacuation for 2 billion inhabitants of nine planets to 14 different planets starting with two shuttle craft (carries 1,000) and the capability to build two more every month. The home star will nova (explode) in one year. All the other planets are varying distances from the home world.

A Robert Half web developed submitted this brainteaser to the Experts Exchange forum.

9. If I gave you $40,000 to start a business, what would you start?

This question appeared on Glassdoor’s annual list of oddball interview questions this year, from a job candidate for HubSpot.

10. How big is the room we’re sitting in?

This question was submitted to the Experts Exchange forum by an IT manager at Esselte Group.

The bottom line? Brainteasers can help you glean insights about how a candidate thinks and responds to pressure–but don’t put too much weight on them.

“If you’re in tech or engineering, brain-teasers are probably appropriate interview questions, but only if they’re given as much credence as the rest of the questions,” McAdams said. “Use them, but don’t fetishize them.”