An Indian chief had three wives, and all of them were pregnant.

   Wife #1 gave birth to a beautiful boy, and the chief was very pleased. He
built his wife a tipi made of buffalo hide. The whole tribe
knew it was a good omen.

   Wife #2 gave birth to a beautiful boy, and the chief was very pleased. He
built this wife a tipi made of antelope hide. The whole tribe
knew it was a good omen.

   Wife #3 gave birth also, and the chief was very pleased. He built this
wife a two-story tipi made of hippopotamus hide. The tribe was
puzzled by this strange tipi.

   Soon a bright young brave reasoned that the chief's wife had given birth to
twin boys, and he said so.

   The chief replied "That is correct, but how did you figure it out?

   The brave answered "Simple algebra. The sons of the squaw of the
hippopotamus hide is equal to the sons of the squaws of the other
two hides."