Compute expected arc length on a circle

Read the full interview experience this question came from →

Quick Overview

This question evaluates understanding of geometric probability, order statistics on a circle, and expectation computation for continuous random variables.

Compute expected arc length on a circle

Company: DRW

Role: Quantitative Trader

Category: Statistics & Math

Difficulty: easy

Interview Round: Online Assessment

On the unit circle (radius \(1\), centered at the origin), pick **three** points independently and uniformly at random on the circumference. These three points partition the circle into three circular arcs. Let \(L\) be the **length of the arc (along the circumference)** that contains the fixed point \((1,0)\) (angle 0). Compute \(\mathbb{E}[L]\).

Overview: This question evaluates understanding of geometric probability, order statistics on a circle, and expectation computation for continuous random variables.

Read the full DRW Quantitative Trader interview experience this question came from

|Home/Statistics & Math/DRW
DRW logo
DRW
Nov 22, 2025
easyQuantitative TraderOnline AssessmentStatistics & Math
7
0

On the unit circle (radius 11, centered at the origin), pick three points independently and uniformly at random on the circumference. These three points partition the circle into three circular arcs.

Let LL be the length of the arc (along the circumference) that contains the fixed point (1,0)(1,0) (angle 0).

Compute E[L]\mathbb{E}[L].

Loading comments...