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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.

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752 matching entries · page 1 of 16

Probability and Statistics · Easy

Collecting Stickers

Supported standard problem · Match confidence: high

Jane Street · Topic guidance
About this question’s source match

The title and category fit the established public problem structure; the hidden catalogue parameters have not been established. Exact Trading Interview wording, numbers and requested subparts remain unverified; this is not claimed to be the hidden source question.

An album has 10 sticker types. Every packet contains one independent uniformly chosen type. Duplicates are kept. Find expected packets to complete the album, and expected additional packets when exactly 8 distinct types are already collected.

Assumptions and constraints

  • Use the random mechanism explicitly specified in the prompt.
  • Give exact expressions where possible and justify each requested result.

Examples

already 9 types
→ 10 more packets in expectation

Each packet succeeds withprobability 1/10.

Company preparation relevance

These links connect this exercise to companies’ public examples or stated interview topics. They do not establish that a company asked this exact Learnr question.

  • Jane Street

    Official topic guidance

    Topic overlap: expected-value decisions “Cash or Reroll”, additive waiting expectations “Collecting Stickers”, and dependence in “Variance of Two Variables” connect to the guide’s expectation, linearity and independence sections.

    Probability & Markets — official guide ↗
    Evidence scope and uncertainty

    General probability preparation; numerical tasks and structures beyond those topics are Learnr choices.

    These are Learnr-authored exercises selected for topic overlap. The company does not name these catalogue titles or verify that these exact questions were asked.

References

Read the supporting material without leaving your question.

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