Mental math practice, with a path to the trading desk.
That’s a live drill on the right, not a screenshot — start typing and the clock runs. Free, no signup. Follow the path and it becomes full prep for quant, sales & trading, and structuring interviews: brainteasers, market making, options and volatility. 31 categories, unlimited questions, and the method behind every answer.
Click in and start typing — the clock starts with you.
If you’re prepping for an interview, it comes in three rounds
Quant, sales & trading, and structuring interviews all test the same three things, and most candidates only prepare for the first. Getting quick at arithmetic does nothing for a probability round, and neither prepares you to price a knock-out.
The online screen
10 categories
Timed arithmetic under negative marking — percentages and missing operands, not just addition.
- Arithmetic
- Numeric fluency
The interview round
9 categories
Sequences, estimation, and the puzzles you talk through out loud: dice, expected value, stopping problems.
- Reasoning
- Probability & games
The desk round
12 categories
What the seat actually needs — quoting a market, bond risk, option structures, and volatility.
- Trading desk
- Options & exotics
- Volatility & Greeks
Every question knows how it should have been solved
Each problem is constructed rather than pulled from a fixed bank, so the engine can inspect the numbers it just made and name the shortcut a trader would use on them. Miss a question and you get the technique, not a red cross.
A book makes 1% in the average month with a monthly volatility of 10%. Approximating √12 as 3.5 and ignoring the risk-free rate, what is its annualised Sharpe ratio?
= 0.35
Monthly Sharpe first: 1/10 = 0.1. Then annualise by √12 ≈ 3.5, not by 12: 0.1 × 3.5 = 0.35. The long way agrees — the annual return is 12 × 1 = 12% against an annual vol of 10 × 3.5 = 35%, and 12/35 = 0.35. The trap is annualising the return and leaving the volatility monthly, which inflates the ratio by √12.
Priced for a deadline, not a habit
Just here to keep your mental math sharp? The arithmetic drills stay free permanently. Prepping for an interview? A 14-day pass unlocks the other 25 categories — probability, options, volatility, bond risk — every assessment simulation, and the method for each question you miss.
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