Rapid-fire arithmetic: solve as many problems as possible before time runs out. The definitive quant mental math trainer.

Configurable arithmetic drill: choose your operations, difficulty, and duration. Good for warming up.

Comprehensive reference: squaring, FOIL, ×11, ×25, fractions, BS approximation, Rule of 72, and more.

Flip through a shuffled deck — predict if each card is higher or lower. Tests Bayesian updating of conditional probabilities.

Pick a 2-flip pattern (HH, HT, TH, TT). Race the computer — whose pattern appears first? Covers Conway's algorithm.

Classic probability problems from real quant interviews. Bayes, birthday paradox, combinatorics, and more.

Identify the next number in numerical and logical sequences. Common in Citadel and Goldman screens.

Given a bet or game description, calculate the expected value. 15 problems, scored by closeness.

Roll 5 dice, choose which to keep, reroll the rest (2 rerolls). Maximize your sum. Optimal stopping problem.

You're shown a biased coin's true probability. Bet your bankroll over 20 rounds. How close to Kelly-optimal are you?

Estimate 25 real-world quantities by order of magnitude. Classic final-round Fermi questions, scored logarithmically.

Quote two-sided markets with real order flow. Manage inventory and PnL over 30-second rounds.

Test your intuition on what moves option prices. Covers delta, vega, put-call parity, and Black-Scholes.

Classic logic puzzles from quant finals: hats, weighing, pirates, and more. Think out loud.

Timed random questions from all tracks. Rate yourself 1-5 after each answer. Tracks your weakest topics and streak.

Interactive sliders for S, K, T, σ, r — watch all 5 Greeks update live with sparkline sensitivity charts.

Random probability puzzles with 90-second clock. Tracks your streak, speed per topic, and best time.

Memorize the full multiplication table to 25×25 with an interactive grid and flip flashcards, then drill rapid-fire recall — addition, subtraction, multiplication, division, and squares — plus mental-math tips.

Spaced repetition flashcards for Greeks, probability, statistics, market making, mental math, ML, and poker math. Built-in SM-2 algorithm.

Pot odds, EV calculations, GTO bluff frequencies, hand equity, and Kelly sizing. The math Jane Street and Optiver actually test.

Quote bid/ask on dice, cards, coins, and earnings surprises. P&L tracked across sessions. The Optiver phone screen format.