- Is there a single shape that will tile a plane aperiodically (see
aperiodic tiling)? An answer
of "no" would imply the existence of a decision method for the domino
problem. The problem, which is named because of the German translation
(ein = "one," stein = "stone") and was not an invention
of the famous scientist, remains unsolved.
- A logic problem invented by Albert
who claimed that 98% of the people of the world couldn't solve it. The
following information is provided:
- There are 5 houses (along a street) in 5 different colors: blue,
green, red, white, and yellow.
- In each house lives a person of a different nationality: Briton,
Dane, German, Norwegian, and Swede.
- These 5 owners drink a certain beverage: beer, coffee, milk, tea,
or water; smoke a certain brand of cigar: Blue Master, Dunhill,
Pall Mall, Prince, or blend; and keep a certain type of pet: cat,
bird, dog, fish, or horse.
- No owners have the same pet, smoke the same brand of cigar, or
drink the same beverage.
- The Briton lives in a red house. The Swede keeps dogs as pets.
The Dane drinks tea. The green house is on the left of the white
house (next to it). The green house owner drinks coffee. The person
who smokes pall Mall rears birds. The owner of the yellow house
smokes Dunhill. The man living in the house right in the center
drinks milk. The Norwegian lives in the first house. The man who
smokes blend lives next to the one who keeps cats. The man who keeps
horses lives next to the man who smokes Dunhill. The owner who smokes
Blue Master drinks beer. The German smokes Prince. The Norwegian
lives next to the blue house. The man who smokes blend has a neighbor
who drinks water.
The question is: Who keeps the fish?