Riddles are a fun way to get students thinking logically and tackling problems that can seem overwhelming at first. In this TED-Ed riddle, students are put in the position of a famous mathematician who has been jailed by his king, but has a chance at freedom if he can figure out which of 12 seemingly identical coins has been counterfeited by a corrupt official.  The video sets up the conditions of the riddle at the beginning and the answer comes at 1:18.

This second riddle is a classic river crossing problem with unique limitations that force students to think through various options. The video even offers some problem solving strategies, that could be used as clues. The answer comes at 1:04 in this video.

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