Friendship is magic
Probability
Level
4
Sir Erdyi, like most of us, has more than 3 friends. Denote the set of Sir Erdyi's friends by F.
He notices that each pair of persons in F knows exactly one other person in F. Which of the following statements is true?
There is a finite number of possibility for the number of elements of F
It is possible for every friend to know only one person (except him/herself)
There is a friend in F who knows everyone (in F)
None of the above
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1 solution
Here what I imagine is let us say there are 'n' friends in the set F where n>3 (given condition).
Then I started forming pairs starting from 1st person to 'nth' in this manner or format: (Person, Who knows this person).
(1,2), (1,3), (1,4), (1,5), (1,6).....(1,n)
(2,3), (2,4)......(2,n)
. . .
(n-1,n)