Farm Fair Contest
What is the minimum number of weighing operations required to measure 63 kg of wheat, if only one weight of 1 kg is available?
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Shaka Prynne from United States School: Richmond Elementary  Report Abusive 
Your answer:  If I want to minimize trips to teh scale, I'd say 7. 
Explanation:  OK, the scale only weighs 1Kg at a time, but wheat has a uniform density, so I ask my workers to make nine fairly equal piles of wheat. Then I take one pile of wheat and weigh it in 1kg increments. Nine is a good number because it is the largest number you can remember without writing it down. Each pile should weigh whatever it weighs (actually 7kg), and with a weight of 1kg, it's seven trips to the scale. Of course you have the work of shoveling all those piles. 
