Problems

Waiting for Two Heads in a Row

Goldman Sachs · Morgan Stanley · Two Sigma

Expected Flips Until HTH

Birthday Problem Threshold

At Least One Boy

D. E. Shaw

Monty Hall with Four Doors

Positive Test, Rare Condition

Which Coin Did I Draw?

Jane Street

HHT or HTT First?

Jane Street

An Even Number of Heads

Jane Street

A Fair Flip from a Biased Coin

Jane Street · Akuna Capital

P(X > Y) for Two Normals

Citadel

Waiting for Two Sixes in a Row

Citadel Securities

Best of Three or Win by Two?

Susquehanna (SIG) · Optiver

Will the Next Card Be Higher?

Susquehanna (SIG)

Three Dice in Increasing Order

Optiver

Break the Longer Piece

Goldman Sachs

First to Roll a Six

J.P. Morgan

Simulate a Die with a Coin

J.P. Morgan · Jane Street

A Sum of 4 Before a Sum of 2

Goldman Sachs

Product of Two Uniforms Below One Half

Goldman Sachs

Every Even Face Before Any Odd

IMC Trading

Four-Sided or Six-Sided?

IMC Trading

A Seven Somewhere Up to a Million

Optiver

Meeting at the Station

Citadel

One Double-Headed Coin in a Thousand

Goldman Sachs · Squarepoint Capital · Renaissance Technologies

One Third from a Fair Coin

Goldman Sachs

One Fair Coin Among Many

Jane Street · Millennium

51 Coins Against 50

Squarepoint Capital

Will Two Teams Meet?

Five Rings

One of Them Is Named William

D. E. Shaw

A Negative Test with No Base Rate

D. E. Shaw

Three Flips, at Least One Head

Akuna Capital

Waiting for HHT

Jane Street · Deutsche Bank

Real Roots from Random Coefficients

Bank of America