The 10 Most Difficult Interview Brainteasers Ever Asked – Can You Answer Them?

The 10 Most Difficult Interview Brainteasers Ever Asked – Can You Answer Them?

A couple of weeks ago we published a blog called:

7 Interview Brainteasers to Assess Your Interviewee’s Critical Thinking.”

The blog was – although fun – supposed to be dead serious, revealing some top-quality brainteasers for interviewers to use when trying to recruit superstar staff.

This blog is, however, is not so serious.

Rather – we’ve collected the top 10 most outrageous brainteasers that people have actually been asked in interviews. We do NOT recommend using them.

Of course we wouldn’t want to leave you in the lurch so you’ll find links to the answers throughout the post!

No peeking!


1. A Petri Hard Puzzle.

Question 1: “A scientist puts a bacteria in a petri dish at exactly noon. Every minute the bacteria divides into two and doubles in size. At exactly 1 PM the petri dish is full. At what time was the dish half full?” T3 Trading Group.

Click HERE to reveal the answer!

2. Make McClane Proud…

Question 2: “You have a 3-litre jug, a 5-litre jug, and an unlimited supply of water. How do you get exactly 4 litres of water without estimating?” UBS Investment Bank

Click HERE to reveal the answer!

3. A Light-bulb Moment!

Question 3: “A windowless room has 3 light bulbs. You’re outside the room with 3 switches, each controlling one of the light bulbs. If you can only enter the room one time, how can you determine which switch controls which light bulb?” IBankingFAQ

Click HERE to reveal the answer!

4. Is this a yolk?

Question 4: “There are three boxes of eggs. In each box there is either a set of big eggs, small eggs or big and small eggs mixed. The boxes are labelled (shock) LARGE, SMALL and MIXED but each box is labelled incorrectly. What is the least number of boxes you can open to know which eggs are in which box and why?” Bloomberg.

Click HERE to reveal the answer!

5. Are You Seeing Things?

Question 5: “You walk across a bridge and you see a boat full of people, yet there isn’t a single person on board. How is that possible?” Management Consulting Prep

what brainteasers
Click HERE to reveal the answer!

6. A Tick Question.

Question 6: “If you look at a clock and the time is 3:15, what is the angle between the hour and the minute hands?”

A clock face with the second hand ticking

HINT: if your answer seems to easy to be true…it probably is.

Click HERE to reveal the answer!

7. Cabin Fever.

Question 7:  “There’s a cabin in the woods and within it, two men lay dead. The cabin did not burn, but the wood around the cabin did. How did the men die?” Street of Walls

Click HERE to reveal the answer!

8. Word-Play.

Question 8: “What is unusual about the following words: revive, banana, grammar, voodoo, assess, potato, dresser, uneven?” Forbes.

Click HERE to reveal the answer!

9. The Lie Detector Test.

Question 9: “During lunch, 5 of Mr. Bryant’s students visit the supermarket. 

pinnochio's nose growing GIFOne of the 5, stole an apple. 

When questioned…

Jim said: it was Hank or Tom.
Hank said: neither Eddie or I did it.
Tom Said: you’re both lying
Don said: no one of them is lying, the other is speaking the truth.
Eddie said: no Don, that’s not true.

When the shop owner asked Mr. Bryant, he said that three of the boys are always truthful, but two lie all the time.

So – who stole the apple?” Management Consulting Prep.

Click HERE to reveal the answer!

10. You Might Recognise This One..?

a sloth scratching his chinQuestion 10:

“Alive without breath,
As cold as death;
Never thirsty, ever drinking,
All in mail never clinking.”

OK, so this is not necessarily an interview brainteaser…but if interviewers are allowed to ask some of the weird and wacky questions I’ve highlighted above, then surely I can ask this little gem..?

Click HERE to reveal the answer!


Did you get the right answers?

Congrats if you did – I must admit that some of the questions completely mind-boggled me!

Recruiter Pro Tip

If you’re involved in the interviewing process at your business, I urge you not to use these brainteasers (or any similar ones) to assess your candidates.

We prefer a fair combination of the following…

Don’t get me wrong, it’s great to have a laugh and challenge yourself but most companies (including Google) have come to the conclusion that such interview questions are a waste of time.

If you’ve got any brainteasers you’d like to share, feel free to pop a comment below or you could drop us an email or LinkedIn message.

Happy Friday – have a lovely weekend.

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Ronald D Ziegenhorn
Ronald D Ziegenhorn
9 months ago

What they call brain teasers are just trick questions.