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?
Can anyone help me understand?
The problem here is that the riddle tricks you into thinking the total at the end should be 30, but because the herders originally give 30, but then get 3 back, the new total of sheep that changed hands is actually 27. In the end, the troll has 25 sheep and his sons have 2 sheep, 25 + 2 = 27 so all sheep are accounted for.