Neatorama presents our collaboration with Pzzlr, a site where you can always find a riddle to exercise your brain. Can you solve this one?

A set of soccer games is to be organized in a round robin (e.g. every team plays a match against each other one time). If 45 games are played, how many teams participated?

Think you know the answer? Find out at Pzzlr!

Look for a new puzzle here at Neatorama every Wednesday, and check out Pzzlr for a puzzle anytime!

Newest 5 CommentsAbusive comment hidden.(Show it anyway.)I still see triangle numbers and such come up in kids books trying to introduce interesting math or for a visual example of an algebra formula. But there is no emphasis on remembering that since there is enough use for math other than parlor tricks today, and more serious combinatorics efforts are hidden until upper level undergraduate programs or lumped in with basic probability problems. I suppose it is sad for something not to be learned because it is not useful anymore, on the other hand, not so much as long as kids are learning something.

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