Brain Teasers 
 
1. A puzzle to puzzle you 
 
You are the only survivor of a plane crash. You are standing on flat ground. There is nothing around you: no trees, no houses, nothing at all. You try to find out where you are. You leave your start walking and go one km south. You don't see anything at all. So you go one km west. Still nothing. So you go one km north and find you are back to where you started, at the plane crash. How is this possible? 
 
A variation on this puzzle is that you are again lost. This time you go one km north and then one km south, but you are not where you started. 
 
What is going on? How can this be? 
 
2. Numbers game 
 
Think of a 10 digit number that is divisible by 9. Reverse the order of the digits. Is it still divisible by 9? 
 
Think of a 10 digit number that is divisible by 11. Reverse the order of the digits. Is it still divisible by 11?