Turkish NMO First Round - 2012 Problem - 10 {Number Theory}
Source:
July 1, 2012
number theoryrelatively prime
Problem Statement
How many positive integers n are there such that there are 20 positive integers that are less than n and relatively prime with n?<spanclass=′latex−bold′>(A)</span>1<spanclass=′latex−bold′>(B)</span>2<spanclass=′latex−bold′>(C)</span>3<spanclass=′latex−bold′>(D)</span>4<spanclass=′latex−bold′>(E)</span>None