A boy was at a carnival and went to a booth where a man said to the boy, "If I write your exact weight on this piece of paper then you have to give me $50, but if I cannot, I will pay you $50." The boy looked around and saw no scale so he agrees, thinking no matter what the carny writes he'll just say he weighs more or less. In the end the boy ended up paying the man $50. How did the man win the bet?

“The man had a hidden scale.”

The riddle specifically mentions that the boy saw no scale, so the man's ability to weigh the boy using a hidden scale contradicts the information provided.

“The man guessed the boy's weight correctly.”

The riddle states that the man wrote down the boy's exact weight, implying that he didn't guess but rather cleverly framed the bet to ensure he wouldn't lose.

“The boy was tricked into revealing his weight before the bet.”

The riddle does not indicate that the boy revealed his weight; instead, it focuses on the wording of what the man wrote, which was key to winning the bet.