“Mathematics has little surprises that are designed to test and push your mental limits The following 12 simple math problems prove outstandingly controversial among students of math, but are nonetheless facts.
“They’re paradoxes and idiosyncrasies of probability. And they’re guaranteed to start an argument or two. If you’re looking for a mathematical way to impress your friends and beguile your enemies, here’s a good place to start.”
https://www.businessinsider.com/the-most-controversial-math-problems-2013-3#-1
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