IMO Shortlist 1979 problem 16
Dodao/la:
arhiva2. travnja 2012. Let
denote the set
.
is a collection of
different subsets of
, and it is known that any three members of
have at least one element in common. Show that all
members of
have exactly one element in common.
%V0
Let $K$ denote the set $\{a, b, c, d, e\}$. $F$ is a collection of $16$ different subsets of $K$, and it is known that any three members of $F$ have at least one element in common. Show that all $16$ members of $F$ have exactly one element in common.
Izvor: Međunarodna matematička olimpijada, shortlist 1979
Školjka 
