Jane Street Interview Math Practice
"Jane Street interview math practice should focus on probability arithmetic, expected value, market-making estimates, and clear spoken logic."
— WSM Direct AnswerJane Street's own interview material points candidates toward problem solving, probability, statistics, data analysis, and market-style reasoning. The arithmetic is not the whole interview, but weak arithmetic makes every explanation harder.
A bet pays +$12 with 60% probability and -$6 otherwise. Expected value?
▸ About +$4.80.
Multiply 0.6 by 12 for 7.2, then subtract 0.4 x 6, or 2.4. Net EV is 4.8.
You quote a market at 46 / 54 and learn the value is likely 60% of your range. New fair value?
▸ About 51.
The range is 8 points wide. Sixty percent of 8 is 4.8. Add that to 46 for about 50.8.
Odds are 3-to-2 in favor. Approximate implied probability?
▸ About 60%.
Three favorable outcomes out of five total parts gives 3/5, or 60%.
How Wall St Math Helps
Wall St Math gives candidates timed reps on the arithmetic behind EV, percentages, odds, and market updates so interview reasoning stays crisp.