Lewis Carroll's "A tea party"
Computer Science
Level
2
A mayor wants to have a small tea party. He only invited the following:
- His father's brother-in-law
- His brother's father-in-law
- His father-in-law's brother
- His brother-in-law's father
What is the minimum number of guests he invited?
Please note that ANYTHING is possible.
The answer is 1.
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Suppose the mayor's sister is married to his father. Then the mayor's brother, denoted by B1, is the father's brother-in-law. Now suppose that same sister is also married to B1. Assuming another brother of his, denoted by B2, is married to the daughter of that sister, then B1 is B2's father-in-law. So B1 is the mayor's brother's father-in-law. Now suppose the mayor is married to his own daughter. Then he is his own father-in-law, so B1 is his father-in-law's brother. Now suppose B1 has a daughter, D1, and a son, S1. If the mayor married D1, it makes S1 his brother-in-law, making B1 his brother-in-law's father. So B1 could be the only one invited. So the minimum number of guests he invited is 1.