Mental math for trading interviews

Short answer: the mental math test in a trading interview is a timed arithmetic sprint: whole-number addition, subtraction, multiplication and division, often with fractions, decimals and percentages, at a pace of a few seconds per question. You pass it by practising the same format against a clock, daily, until the basic facts are automatic. R3CK0N's sprint and 80-in-8 drills are free versions of that format, with no account needed.

Many quantitative trading and market-making firms screen candidates with a timed arithmetic test. The maths is simple; the time limit is not. Passing is almost entirely a matter of practice.

What the tests usually look like

Formats vary by firm and change over time, so treat this as a general picture rather than a spec:

• A short, hard time limit — often a few minutes for a long list of questions, more than most people can finish.
• Mixed operations — addition, subtraction, multiplication and division in one sitting, not in blocks.
• No calculator and no paper, or very little of either.
• Some tests add decimals, fractions or negative numbers, and some penalise wrong answers — so accuracy matters as much as speed.

The best-known free practice tool is the Zetamac arithmetic game, which runs a two-minute mixed-operation sprint. If you've been using it, R3CK0N works as a complement (how they compare): the same kind of timed mixed drill, plus per-problem timing, a saved history, and dedicated drills for specific techniques.

A practice setup that matches

1. Open Math → Custom. It blends all four operations, and you can weight them — push multiplication and division up if those are your weak spots.
2. Set the timer to 120 seconds.
3. Start on Medium (numbers up to 999, factors up to 99). Move to Hard once your accuracy is consistently high.
4. Do a few runs every day and watch your problems-per-minute trend in the Stats tab.

Where the time actually goes

After each run, R3CK0N draws a bar for every problem, sized by how long it took. For most people preparing for these tests, the pattern is the same: addition and subtraction are fine, and a handful of multiplication and division problems eat half the clock. Fix those specifically:

• Times tables to 12 must be instant. Any hesitation here compounds across every multiplication and division. Times tables practice.
• One digit × two digits should be a single left-to-right step: 7 × 86 = 560 + 42 = 602.
• Two digits × two digits needs a method you don't have to think about. Three methods, with examples.
• Division is multiplication backwards. 378 ÷ 7 is "7 times what?" Split it: 350 ÷ 7 + 28 ÷ 7 = 54. Division speed test.
• Subtraction without borrowing. Round and correct, or count up. Subtraction methods.

How much practice is enough?

Short daily sessions beat occasional long ones — ten minutes a day for a few weeks will do more than a weekend of cramming. Track your score on one fixed setting so you're comparing like with like, and practise under test conditions: no pausing, no paper.

Frequently asked questions

Does R3CK0N cover decimals and fractions?

Partly. The four-operation drills use whole numbers, which is the bulk of most tests. For decimals, the GRE Quant drills in Math mode include fraction to decimal and percentages.

Is it free?

Yes. No ads, no paywall, and no account needed.

For the rest of the interview (a multiple-choice trading sprint with negative marking, probability and expected-value questions, sequences, estimation and a market-making game), see Quant Prep and the quant interview prep guide.