MathDB
x-y<=xy/25 if x,y in A, max |A|

Source: VJIMC 2001 1.1

July 23, 2021
number theorySetsinequalities

Problem Statement

Let AA be a set of positive integers such that for any x,yAx,y\in A, x>y    xyxy25.x>y\implies x-y\ge\frac{xy}{25}.Find the maximal possible number of elements of the set AA.