PIRATES
When the Roman army needed to punish a large number of men, every tenth soldier was executed - hence the word 'decimate'.
You are one of a band of 1,000 mutinous pirates, captured and tied to numbered posts arranged in a circle. The first is to be executed, then each alternate pirate, until only one remains. The last remaining live pirate will be allowed to live. Which number pirate will go free. Which number post would you choose in order to live?