Sam sells bibles in the MIddle East. One day, he loaded hi canoe full of bibles and paddled off down the solitary river which meanders its way through the barren sand.
Sam's customary business practice consists of stacking the bibles on one side of a huge set of balance scales and the nomads piling gold on the other. When the scales balance, the transaction is complete.
One day, Sam met a nomadic group at the edge of the river and began doing business. Unfortunately for Sam, the scales broke. Since there was nothing around but sand, Sam couldn't think of a fair way to weigh the bibles. He was just getting into his canoe to paddle off, when someone had a brilliant idea. What was the idea that would allow them to accurately weigh and exchange the bibles for gold?