MathDB
SMT 2023 Discrete #4

Source:

May 3, 2023

Problem Statement

Michelle is drawing segments in the plane. She begins from the origin facing up the yy-axis and draws a segment of length 11. Now, she rotates her direction by 120∘120^\circ, with equal probability clockwise or counterclockwise, and draws another segment of length 11 beginning from the end of the previous segment. She then continues this until she hits an already drawn segment. What is the expected number of segments she has drawn when this happens?