An indian chief Sitting Bull had three wives, each of whom he got pregnant at the same time.
His first wife gave birth to a boy and Sitting Bull was so happy he built her a teepee made of deer hide.
A few days later, the second gave birth, also to a boy. Again, the chief was delighted so he built her a teepee made of antelope hide.
The third wife gave birth a few days later, but this time the chief kept the details a secret.
He built the third wife two story teepee, made out of hippopotamus hide and then challenged the tribe to guess what had occurred. Many tried, but nobody could work out what had happened. Finally, one young man declared that the third wife had given birth to twin boys.
“That’s true,” said Sitting Bull. “How did you figure it out?”
The man answered, “It’s simple – the value of the wife of the hippopotamus is equal to the sons of the wives of the other two hides.”