Eating Together
Riddle: Two dads and two sons were eating together, for dessert, there were 4 oranges. Each one took an orange, so why was there an orange left over?
Answer: There were two dads and two sons, the Son was the son of the Father and the Father was the son of the Grandfather. The Grandfather was the father of the Father and the Father was the father of his son. That makes two sons and two dads, but actually, only three people were present.
Source: https://www.riddles.com/6711
