Introduction to Logic


There are five houses of different colors next to each other. The inhabitants are of different national extractions, own different pets, drink different beverages, and smoke different brands of cigarettes. Suppose that the following facts are all true.

There is a row of five houses.
The Englishman lives in the red house.
The Spaniard owns the dog.
Coffee is drunk in the green house.
The Ukrainian drinks tea.
The green house is immediately to the right of the ivory house.
The Old Gold smoker owns snails.
Kools are smoked in the yellow house.
Milk is drunk in the middle house.
The Norwegian lives in the first house.
The man who smokes Chesterfields lives in the house next to the man with the fox.
Kools are smoked in the house next to the house where the horse is kept.
The Lucky Strike smoker drinks orange juice.
The Japanese smokes Parliaments.
The Norwegian lives next to the blue house.
Someone owns a zebra.

Who owns the zebra? What is his nationality? What does he drink? What does he smoke? What color is his house?

This problem is sometimes attributed to Albert Einstein and sometimes to Lewis Carroll. The version here is taken from Life International 1962. The problem and its solution are easily found on the Internet. Resist the temptation to look them up until you have had a chance to solve the problem for yourself. It is not very difficult if you use Relation Model Checking techniques.