← 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

Brain Teasers · Easy

Wristband Pairs

Original interpretation · Match confidence: medium

Company use unverified
About this question’s source match

Title plus Brain Teasers / Pigeonhole Principle supports the stated family or explicit original interpretation; each source’s scope is limited below. The title and Pigeonhole Principle subcategory support matching-color pairs, but do not specify available colors or what constitutes a pair. Those mechanics are explicitly supplied as an original interpretation.

Original Learnr interpretation; the private catalogue statement is unverified. A bag contains10 red,10 blue and10 green wristbands. You draw blindly without replacement. A pair means any two wristbands of the same color; no left/right distinction applies. What is the minimum number of draws guaranteeing a pair regardless of draw order?

Assumptions and constraints

  • All measurements, permissions and rules in the statement are exact.
  • No unstated constraints apply.
  • Solve the fixed instance and justify the construction or calculation.

Examples

The scenario stated in the question.
→ 4

Four draws guarantee a pair, and three do not.

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.