← Quant playground

Free practice library

Interview practice

Solve complete questions with progressive hints, worked solutions and Python implementations. Each question explains its assumptions and source match. Original interpretations are labelled explicitly.

752

Ready to practise

174

Not yet playable

926

Catalogue titles

Public standard problems and original exercises; hidden Trading Interview questions have not been verified.

174 titles have been investigated but remain unresolved. Their missing details are recorded without adding substitute exercises. Every playable question has a guided animated answer; selected questions also have custom diagrams.

Practise Learnr’s own questions →Follow a role-specific curriculum →

752 matching entries · page 1 of 16

Probability and Statistics · Easy

Gambler's Ruin #1

Original interpretation · Match confidence: medium

Company use unverified
About this question’s source match

Gambler ruin is standard, but the numbered #1 title does not identify whether the hidden variant concerns fair/biased odds, probability or duration. This explicitly chosen fair variant is original. The hidden Trading Interview wording, parameters and requested subparts have not been verified.

A gambler starts with 3 units and plays independent fair bets, winning or losing one unit each time. Play stops at capital 0 or 10. Find probability of reaching 10 before 0 and expected number of bets. Generalize from starting capital i and target N.

Assumptions and constraints

  • IID fair bets of exactly one unit; no borrowing.
  • N positive integer; 0<=i<=N integer.

Examples

i=1,N=2
→ success=1/2, expected bets=1

Either first bet hits a boundary.

Company evidence · unverified

No company-specific source has been matched to this exercise. Its references support the topic or solution method; they do not establish employer use.

References

Read the supporting material without leaving your question.

Catalogue metadata captured 2026-10-12. Metadata source.