I just read Dr. No by Percival Everett. It contains a maths riddle that I cannot get my head around. I tried searching online but I couldn't find any answers.
Here's the riddle:
There are three sheepherders who come to a bridge controlled by a troll and his two sons. He demands of them thirty sheep before they can pass. Each shepherd cuts out ten sheep from his flock and they give them to the troll. Once they have crossed, the troll decides that he should only have asked for twenty-five. He sends his sons after the men with five sheep. The sons decide to keep one sheep each and give three back to the herders. They do. Now it is the case that each shepherd has paid only nine sheep. Nine times three is twenty-seven. The trolls kept two. Twenty-seven plus two is twenty-nine. Where is the missing sheep?
The total amount given to the troll and sons were 27 sheep (25 and the sons kept 2).
Where it gets confused is saying "The trolls kept 2" as if this were 2 more sheep on top of the 27 sheep. This leads to you erroneously getting to 29 sheep somehow. The 2 sheep are part of the 27, you can't do this.
The 3 other sheep out of the original 30 are now with the shepherders after the sons came and returned them.