Solo, or race a real run?
20 cards, one at a time. Take a card first and it is +1 - answer wrong and it is −1 and gone. One shot per card, so do not buzz until you are sure.
A fixed timer either cuts the hard categories off mid-thought or drags once the easy ones come up. A 20-card deck self-adjusts: fast play finishes fast.
Mental math for trader screens, on a clock that subtracts
Almost every trading screen opens with timed arithmetic, and most of them mark a wrong answer down rather than ignoring it. This is that round to practise against, on its own, in runs short enough to do several in a sitting.
How the scoring works
A card taken correctly is +1. A card answered wrong is −1 and it is gone. A card nobody claims inside ten seconds expires and scores nothing. That is the same shape as the real round’s marking, and it is the part that changes how you should play: when a wrong answer costs you a mark, a guess you are not confident in is worth less than a skip.
Most people who miss the threshold on the real thing are not too slow. They are fast and slightly inaccurate, and the negative marking quietly takes back what the speed earned. Practising against a scoreboard that subtracts is the only way to feel that.
Why a deck rather than a straight timer
Twenty cards dealt one at a time, rather than eight minutes of whatever comes up. A fixed timer has a flaw as a practice tool: it cuts you off mid-thought on a hard category and then drags once the easy ones arrive, so the run length tells you nothing. A fixed deck self-adjusts. Play fast and you finish fast, and the time you took is a clean measure you can compare against your last run or against a recorded run of someone else’s.
The per-card ten second expiry does the job the overall clock does on the real test: one stumper cannot stall the whole run.
What it drills
The problem types are the ones these rounds actually ask: two and three digit addition and subtraction, multiplication, fast division, decimals, and the full fraction set, including reducing. Every problem is generated rather than drawn from a fixed bank, so there is nothing to memorise between runs.
The best known version of this round is Optiver’s 80 in 8 - 80 questions in 8 minutes, about six seconds each. This deck is deliberately shorter and a little looser than that, because the point is reps you will actually repeat. If you are preparing for that specific test, the Optiver page below is the one built for it.
How to train for it
Accuracy first, speed second, in that order. Run decks until you are not dropping cards to careless errors, whatever that costs you in time. Only then push the pace. Speed built on top of shaky arithmetic is worth negative marks on a paper that subtracts, which is the one thing a plain stopwatch will never tell you.
Work the categories you avoid. Fractions and fast division are where most people lose marks, and they are the two that improve quickest with reps. When a full deck stops producing errors, go and sit a whole screen rather than more of this.
Optiver 80 in 8 practiceSit a full timed screenDrill strategy and category tips
About Arithmetic Drill
A 20-card flashcard race across twelve arithmetic categories - play solo or race a ghost recording of a real past run.
The drill deals a fixed deck of 20 cards, one at a time. Every card is a freshly generated problem from one of twelve categories: long addition (three-digit plus three-digit), long subtraction, two-digit by two-digit multiplication, fast division (always exact), decimal addition, subtraction, and multiplication, and five fraction operations - add, subtract, multiply, divide, and reduce to lowest terms. Type your answer and press enter; there is no second attempt on a card.
You can play solo or race a ghost - a recording of a real past run on the exact same deck. The deck is rebuilt from a shared seed, so the ghost sees the same cards in the same order and claims each card at the moment its player actually answered it. If the ghost buzzed in wrong on a card, it eats the penalty and the card stays live for you.
Each card has a 10 second timeout so one stumper cannot stall the race. A card nobody claims simply expires. Fraction answers accept either "a/b" or a decimal, but reduce-fraction cards require the exact reduced form - 4/8 does not pass for 1/2. Decimal answers are graded with a small numeric tolerance, whole-number answers by exact match.
Why quant interviews test this
Timed arithmetic under pressure is the front door of trading interviews. Zetamac-style speed tests and firm-specific equivalents at market-making firms filter on exactly this skill: many small computations, fast, with a penalty for errors. Traders do not do long division all day; fluent arithmetic frees working memory for the decision.
The race format here mirrors the culture: in a trading interview, an answer that is fast and right beats one that is slow and right, and one that is fast and wrong is worse than silence. That is precisely the +1 / -1 / pass structure of this drill.
The Arithmetic Drill guide covers how scoring works, the strategy that wins, a worked example and the mistakes most players make.
More Drills games
- Fermi Estimation (Classic) - Quote a low-high range on ten real-world estimation questions - points for containing the truth, more points for a tight range.
- Sequence Sprint - Find the rule and type the next number - freshly generated arithmetic, geometric, square, alternating, and Fibonacci-style sequences.
- Duck Duck Dash - An endless runner through a sunny field where the only way to hop is answering a mental-math question - one collision ends the run.
- Likelihood Ranking - Order outcomes from most to least likely - student score tables, distributions, dice and card events, Poisson arrivals, urns, and scatter plots.
- Crossroad Multitasker - A duck at a 4-way crossroad and four corner math pods - answer whichever question is live as it switches unpredictably between the two streams.
- All Drills practice
- Every game guide