Whose draw is larger?

MediumProbability~6m

Jimmy picks a number uniformly at random from {1,2,,1000}\{1, 2, \dots, 1000\} and, independently, Simon picks uniformly from {1,2,,3000}\{1, 2, \dots, 3000\}. What is the probability that Simon's number is strictly larger than Jimmy's?

Show hints (2)+
  1. Condition on Jimmy's value jj: P[Simon>j]=(3000j)/3000\mathbb{P}[\text{Simon}>j]=(3000-j)/3000.
  2. Average over j{1,,1000}j\in\{1,\dots,1000\} using j=11000j=100010012\sum_{j=1}^{1000} j=\tfrac{1000\cdot1001}{2}.

Answer

Reveal answer →

0.8332 (± 0.002)

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Asked at: Citadel, DRW

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