Logic Riddles

Question: How many letters are in the answer to this riddle?

Question: Tom wants to send Sally an expensive ring through the mail because they live thousands of miles apart. The only problem is that everything sent through the mail is stolen unless there is a lock put on it. Both Tom and Sally have plenty of locks and keys but they don't have any of the same locks or keys.

How can Tom send Sally the ring without it getting stolen?

Question: Flora killed several thousands of people without mercy. Afterwords, Flora disappeared and was never seen again. Yet the police never pursued her.Why?

Question: It takes ten men ten hours to build a certain wall. How long does it take five men to build the same wall?

Question: When you're given one, you'll have either two or none?