MathDB
Speed P10

Source:

October 16, 2021
MOAA 2021speed

Problem Statement

Let ABCDABCD be a unit square in the plane. Points XX and YY are chosen independently and uniformly at random on the perimeter of ABCDABCD. If the expected value of the area of triangle AXY\triangle AXY can be expressed as mn\frac{m}{n} for relatively prime positive integers mm and nn, compute m+nm+n.
Proposed by Nathan Xiong