1979 USAMO Problems/Problem 5
Revision as of 20:17, 16 August 2011 by Mrdavid445 (talk | contribs) (Created page with "==Problem== Let <math>A_1,A_2,...,A_{n+1}</math> be distinct subsets of <math>[n]</math> with <math>|A_1|=|A_2|=\cdots =|A_n|=3</math>. Prove that <math>|A_i\cap A_j|=1</math> ...")
Problem
Let 
be distinct subsets of ![$[n]$](http://latex.artofproblemsolving.com/0/d/e/0deff9086fd7840ef23860f5bc924f1d4d2d2310.png)
with 
. Prove that 
for some pair 
