Logical Thinking

Here is a nice exercise I´ve been using for ages (apologies to whoever I originally stole it from). The idea is to apply logic to a number of facts given in a story and then test the truth of your conclusions. After reading the story, mark each statement with 'T' if it is definitely true, 'F' if it is definitely false and '?' if there is insufficient information to make a decision. Once you have given an answer, don't go back and change it after reading the subsequent statements.

The old man had just turned off the lights in the shop and was preparing to lock up when a youth appeared and demanded money. The owner opened the cash register; the contents were grabbed, and the man ran away. The police were informed immediately.

1. A young man appeared after the lights had been turned off.
2. The old man was preparing to go home.
3. The robber demanded money.
4. Someone opened the cash register.
5. The robber demanded money from the owner.
6. The person who opened the cash register was a man.
7. The cash register contained money, but we are not told how much.
8. The gender of the owner was not revealed in the story.
9. The robber did not demand money.
10. After the young man grabbed the contents of the cash register, he ran away.
11. A young man appeared after the lights had been turned off.
12. The robber was a man.
13. The owner was a man.
14. The owner appeared and demanded money.
15. The man ran away after he had demanded money. 

If anyone wants to know my answers to this one, please let me know.