Mental Math vs Market Making Interviews
How mental math supports market-making interviews without replacing quote judgment, spread choice, inventory awareness, and update discipline.
Candidates who over-focus on arithmetic and under-practice quote decisions.
Arithmetic supports the quote
Market-making interviews use arithmetic for midpoint, spread, probability price, and PnL. Those numbers matter because they affect a quote or risk decision.
Market making adds judgment
A correct fair value does not tell you spread, size, or skew by itself. Uncertainty, inventory, and adverse selection still matter.
Concrete example
If fair value is 50, mental math can produce the midpoint. Market-making judgment decides whether 49 at 51 or 45 at 55 fits the state.
Practice balance
Do arithmetic drills until mechanics are stable, then practice live quote loops where each calculation leads to a bid, ask, or update.
Common mistakes
Candidates often compute quickly and quote too tightly. Arithmetic is useful only when the quote also reflects uncertainty and risk.
Practice the pattern
Use the LeetQuidity curriculum and calibration to turn this topic into a focused practice plan.