Think you're good at maths? Try solving this viral brain teaser involving 9
While some tried providing a solution to the viral maths brain teaser, others shared that it was hard for them to solve.
Do you think brain teasers are fun to solve, especially when they are the ones that leave most people stumped? Here is one such puzzle that can leave you scratching your head. Do you think you can solve the puzzle like a pro?

“What's the solution to this?” reads the caption posted along with the image. The visual shows four 9s written with blank boxes between them. A text insert on top of the image reads, “Can you arrange 4 nines to make it equal to 100 with any mathematical operation?”
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Take a look at the brain teaser here:
The post was shared some 11 hours ago. Since then, the post has accumulated nearly 2,300 upvotes. The viral share has also prompted people to post varied comments.
What did Reddit users say about this quiz?
“If you allow multi-digit numbers, 99+(9/9) works. If they must all be individual 9s and using only +-*/, I don’t think it is possible,” posted a Reddit user.
“Derive the first and third 9 to make them into 0's, then factorial them to make them 1's. Then add the two remaining 9's to each 1 to get two 10's. Then multiply the two 10's and you get 100,” suggested another.
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“Let * be the left associative operation such that 9 * 9 = 100, and 100 * 9 = 9. 9 * 9 * 9 * 9 = 100 * 9 * 9 = 9 * 9 = 100,” joined a third.
“I’m assuming you’re not allowed to combine digits, for example using 99 + 9/9. There’s still many solutions depending on what operations you’re willing to consider, although technically at a certain point you could just arbitrarily define operations,” wrote a fourth.
What are your thoughts on this brain teaser? Did you manage to solve it?
ABOUT THE AUTHORTrisha SenguptaTrisha Sengupta works as Chief Content Producer at Hindustan Times with over six years of experience in the digital newsroom. Known for her ability to decode the internet’s most talked-about moments, she specialises in high-engagement storytelling that bridges the gap between viral trends and traditional journalism. Throughout her tenure, Trisha has focused on the intersection of technology, finance, and human emotion. She frequently covers personal finance and real estate struggles in hubs like Gurgaon, Bengaluru, and Hyderabad, while also documenting the unique challenges of the NRI experience. Her work often highlights the movements and philosophies of global newsmakers and personalities like Elon Musk, Mukesh Ambani, Nikhil Kamath, Dubai crown prince, and MrBeast. From reporting on Amazon or Meta layoffs and startup culture to the emergence of AI-driven platforms like Grok and xAI, she provides a grounded and empathetic perspective on the stories shaping our world. When not decoding the internet, Trisha is likely offline: lost in a book, exploring a historical ruin, or navigating the world as a solo traveler. She balances her fast-paced career with family time and a healthy dose of curiosity, currently trading her "human" sources for silicon ones as she masters AI to future-proof her storytelling.Read More

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