A collection of challenging quizzes for adults [Difficult]
Feeling the urge to tackle a brain-busting puzzle that seems impossible—“No one could solve this!”—might be a uniquely adult kind of curiosity.
But why do puzzles and riddles that hinge on sudden insight make your heart race? It’s because your brain is seeking that moment of activation.
This time, we’ve handpicked challenging problems for adults that test flexible thinking and ideas unconstrained by common sense.
Don’t overthink them—try looking from a slightly different angle.
The “aha!” moment is surely waiting for you.
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Challenging Logic & Exam-Type Quizzes (For Job Applicants, Examinees, and Geniuses) (11–20)
IQ test
Let’s try tackling problems from a genius group that only the top 2% of the population can join.
Here’s an introduction to an intelligence quotient (IQ) test.
It’s a great test idea for when you have some time before an appointment or if you’re interested in IQ.
There are three questions in total, and each section has a time limit.
Take your time to focus and think carefully.
After each time limit, you’ll get the answers along with explanations of the reasoning, so you won’t be left feeling unclear for the rest of the day.
Loosen up your mind and give it a try!
Google’s entrance exam
Google is a global giant, and it’s said that the questions on its entrance exam are notoriously difficult.
This content challenges you with those exam-style problems as a quiz, letting you gauge the level of your knowledge and creativity.
Since the problems include complex steps—like considering conditions and then calculating—let’s set time limits tailored to the participants.
Because calculation-heavy questions inevitably take time, it might be interesting to deliberately choose problems solvable with just memory and creativity, and make it a speed-based competition.
A quiz that even Harvard graduates can’t get completely right
These are problems said to be difficult even for graduates of Harvard University, which is globally associated with high academic ability.
You’re asked to carefully read and unravel story-like questions to arrive at the answer, testing your attention to detail.
Some tasks require finding answers from animations, others involve spotting oddities in the wording—because the formats are so diverse, the key is to think from multiple angles.
Let’s approach each problem by also judging whether it demands more thinking or more observation, and proceed accordingly.
A quiz that 95% of adults can’t solve
You’ve probably been seeing phrases like “Only X% of people can solve this!” more and more in quiz videos on social media and video sites.
Even when you think, “What a clickbait line,” hearing that only 1% got it right can make you a bit competitive and want to give it a try.
How about you? The quizzes featured here are all the kind that “only 95% of adults can solve.” Even if you’re not a big quiz fan, it kindles your competitive spirit, doesn’t it? There are straightforward calculation problems as well as slightly tricky ones—plenty of satisfying challenges.
If you’re confident in your quiz skills, give them a go!
100 marbles
This is an extremely difficult problem that was reportedly used in a Microsoft hiring exam.
There are two boxes and a total of 50 red marbles and 50 blue marbles.
When dividing the marbles between the two boxes, the question is how to arrange them to maximize the probability of drawing a red marble.
What do you think? The answer feels a bit unexpected, but by not fearing imbalance and making this choice, you actually get better results.
I suspect this test is meant to see whether you can view things from a perspective that overturns conventional wisdom.
