There is a tale from the Middle Ages about a magic pebble, called the touchstone, that when rubbed against any metal, would turn the metal into gold. It was said that this pebble could be found on the shores of the Black Sea. It looked like any other pebble on the beach. The only difference between the touchstone and the other pebbles was that it was warm to the touch, and all the others felt cold. What does this story have to do with teaching mathematics? Read more.
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