Problems

118 curated questions across 15 topics, each with hints and a worked solution, including at 24 firms.

– of 118 solved

Easy –/53Medium –/52Hard –/13

/

32 results

Probability & Combinatorics

Easy#3
Birthday Problem Threshold
Probability · Numerical · 5 min
Easy#4
At Least One Boy
D. E. Shaw
Probability · Multiple choice · 3 min
Easy#50
An Even Number of Heads
Jane Street
Probability · Numerical · 3 min
Medium#55
A Fair Flip from a Biased Coin
Jane Street · Akuna Capital
Probability · Numerical · 6 min
Easy#74
Simulate a Die with a Coin
J.P. Morgan · Jane Street
Probability · Free response · 6 min
Easy#85
A Seven Somewhere Up to a Million
Optiver
Probability · Numerical · 3 min
Easy#96
One Third from a Fair Coin
Goldman Sachs
Probability · Free response · 5 min
Easy#115
Waiting for HHT
Jane Street · Deutsche Bank
Probability · Numerical · 5 min

Easy#11
Hats Returned at Random
Expected Value · Numerical · 4 min
Medium#13
Seeing Every Face
Expected Value · Numerical · 6 min
Hard#67
Tying Spaghetti into Loops
Hudson River Trading
Expected Value · Numerical · 10 min
Easy#72
Counting Switches in Coin Flips
J.P. Morgan
Expected Value · Numerical · 3 min
Easy#102
Average Maximum of Two Uniforms
Squarepoint Capital
Expected Value · Numerical · 3 min

Medium#14
Four Crossers, One Lamp
Brain Teasers · Numerical · 8 min
Easy#15
Measuring 45 Minutes with Two Ropes
Brain Teasers · Free response · 6 min
Medium#57
Guess 100 Flips with One Question
Jane Street
Brain Teasers · Multiple choice · 5 min
Medium#93
A Hundred Ants on a Stick
J.P. Morgan
Brain Teasers · Numerical · 7 min
Medium#97
Fastest Three of 25 Horses
Goldman Sachs
Brain Teasers · Numerical · 8 min
Easy#105
Most Pizza Slices from Ten Cuts
Five Rings
Brain Teasers · Numerical · 3 min
Easy#112
Right Angles on a Clock
WorldQuant
Brain Teasers · Numerical · 3 min

Easy#111
Determinant of a Random Symmetric Matrix
WorldQuant
Linear Algebra · Numerical · 4 min

Medium#44
Standard Error of a Monte Carlo π
Numerical Methods · Numerical · 6 min
Hard#45
Monte Carlo European Call
Numerical Methods · Coding · 20 min
Medium#46
When Do Antithetic Variates Help?
Numerical Methods · Multiple choice · 6 min