The Old Mission Capital Probability & Mental Math interview is stage 2 of 4 in the Old Mission Capital interview process, after the Online Assessment. Format: 45-60 min - video. Core probability, expectation, statistics, and mental math under time pressure, with follow-ups.
Preparing for this round? Practice the 40 questions mapped to the Old Mission Capital Probability & Mental Math, with worked solutions. A free account saves your progress.
What the Probability & Mental Math tests
This is the heart of the trading screen.
QuantVault maps 40 practice problems to this round. By topic, the biggest groups are probability (24), expectation (12), statistics (4); by difficulty, 21 easy, 19 medium and 0 hard. 40 of them were reported by candidates who interviewed at Old Mission Capital, most recently in Jun 2026.
- Trader technical rounds run 45 to 60 minutes: mental maths, probability, estimation, put-call parity and a live market.
How to prepare for the Probability & Mental Math
- Estimate first, then formalize.
- Drill mental math -- fast arithmetic, fractions, and EV.
- Expect follow-ups that extend the problem.
Further reading: Mental math for trading interviews · How quant superdays work · Behavioral questions at trading firms · Market-making game interview guide.
Question types in this round
The 3 largest question types in the Old Mission Capital Probability & Mental Math practice set; across them the most common sub-topics are discrete probability, conditional probability, independence, expected value, combinatorics, Bayes' theorem. The questions themselves, with worked solutions, are in the round practice.
Probability24 in this round
Expectation12 in this round
Statistics4 in this round
Prepare with QuantVault
The same round at similar firms
Compare with similar firms
Frequently asked questions
What is the Old Mission Capital Probability & Mental Math interview?
It is stage 2 of 4 in the Old Mission Capital interview process, after the Online Assessment. Format: 45-60 min - video. Core probability, expectation, statistics, and mental math under time pressure, with follow-ups. This is the heart of the trading screen.
How long is the Old Mission Capital Probability & Mental Math interview?
Candidates report: 45-60 min - video.
What questions come up in the Old Mission Capital Probability & Mental Math interview?
The practice set QuantVault maps to this round centers on probability, expectation, statistics.
How should I prepare for the Old Mission Capital Probability & Mental Math interview?
Estimate first, then formalize. Drill mental math -- fast arithmetic, fractions, and EV.
What comes after the Probability & Mental Math?
The ETF, Options & Market-Making Round (stage 3 of 4). Format: 45-60 min - trading intuition.
Practice the Old Mission Capital Probability & Mental Math round
Work the 40 mapped practice problems with progress tracking, then move to the next stage of the Old Mission Capital funnel.