The pieces with the same color in left figure have the same size as in the ones in the right figure. In the right image the pieces are only ordered differently. How to explain the hole in the right image?

How can you put (without using glue or something like that) ten nails on the head of a standing nail? The final construction should be stable.

There are 5 houses in 5 different colors. In each house lives a person with a different nationality. The 5 owners drink a certain type of beverage, smoke a certain brand of cigar, and keep a certain pet. No owners have the same pet, smoke the same brand of cigar, or drink the same beverage.

Somebody owns a fish. The question is: who?

Hints:

• The Brit lives in the red house.
• The Swede keeps dogs as pets.
• The Dane drinks tea.
• The green house is on the left and next to the white house.
• The green homeowner drinks coffee.
• The person who smokes Pall Mall rears birds.
• The owner of the yellow house smokes Dunhill.
• The man living in the center house drinks milk.
• The Norwegian lives in the first house.
• The man who smokes Blends lives next to the one who keeps cats.
• The man who keeps the horse lives next to the man who smokes Dunhill.
• The owner who smokes Bluemaster drinks beer.
• The German smokes Prince.
• The Norwegian lives next to the blue house.
• The man who smokes Blends has a neighbor who drinks water.