Pythagoras joke.Ther was this Indian chief, and he had three wives. They slept in the same tent. One on a bear skin, one on a buffalo skin and one on a hippopotamus skin.
After a time the three had children. The one that slept on the bear skin had a baby boy, the one on the buffalo skin had a baby girl, and the one on the hippopotamus skin had a baby boy and a baby girl, proving that the squaw on the hippopotamus is equal to the sum of the sqaws on the other two hides!!!