To protect his country a king decided to build a wall made out of stone along the border. The wall had to be 3 meters thick and 5 meters high. The border of the country has a length of 500 kilometers. Assuming that one cubic meter of stone weights about 3000 kg, how much heavier becomes the earth by building this wall?

What question do you ask all day, but the answer is always different.

At a nice sun shiny day, a man rowed with his boat to an island in the middle of a big lake. On the island he caught some fish. Then he decides to return with his rowing boat. After 10 meters of rowing he looks behind him, but to his big surprise there is no island anymore. What happend to the island?