Probability & EV Practice
Dice, coin and card probability plus expected-value calculation, on its own — today's free daily drill is a rotating set from a 180-day pool. No signup, runs entirely in your browser.
15 questions · 3 minutes · today's set
Dice, coin, and card probability plus quick expected-value calculations. +1 per correct answer, −1 per wrong answer, skips are free. Same 15 questions for everyone today — a rotating daily set from a fixed 180-day pool.
Today's set comes from a fixed 180-day rotation — the app generates a truly new set every day. Answers accept decimals or fractions (e.g. 0.25 or 1/4).
What this drill trains
Six question types, each a common building block of the brain-teaser and market-making rounds later in the interview pipeline:
| Dice-sum probability | e.g. P(sum of two dice = 7) — 6 of the 36 equally likely outcomes work, so 6/36 = 1/6. |
|---|---|
| Die-roll expected value | e.g. EV of one fair 6-sided roll — (1+2+3+4+5+6)/6 = 3.5. |
| Coin-flip runs | e.g. P(3 heads in a row) — each flip is independent, so (1/2)³ = 1/8. |
| Card draws | e.g. P(drawing an Ace from a standard 52-card deck) — 4/52 = 1/13. |
| Binary-bet EV | e.g. a bet paying +$10 with probability 0.4 and −$5 with probability 0.6 — EV = 0.4(10) + 0.6(−5) = +$1, so it's worth taking. |
| "At least one" / "never" probability | e.g. P(at least one 6 in 4 rolls) — easiest via the complement: 1 − (5/6)⁴ ≈ 0.52. |
Why this matters beyond the drill itself
Probability and EV aren't a self-contained topic that stops once the numerical screen ends — they're the same toolkit interviewers lean on in brain-teaser rounds and the reasoning behind why negative marking changes test strategy in the first place. The full prep guide covers both in more depth, and the Robot Games drill is a direct, timed application of the same EV-sign judgment against a live decision instead of a typed number.
Want number sequences instead?
That's a separate skill with its own daily drill — see Number Sequence Practice. Or try the original combined 60-question Sequences & Probability test.
Related practice
- Robot Games — Play/Pass EV decisions under a live clock
- Quant interview brain teasers — worked probability & EV puzzles
- How to prepare for a quant trading interview — the full pipeline and a study plan
FAQ
What kinds of questions are in the daily drill?
15 questions in 3 minutes: dice-sum probability, die-roll expected value, coin-flip runs, card draws, binary-bet EV, and "at least one" / "never" run probability. Answers accept decimals or fractions.
What's a good score on this drill?
11 of 15 is a comfortable bar here — this is a daily habit-building tool, not a firm's actual cutoff, so there's no official pass mark to chase. Once you're consistently above that, the app's full-length, firm-specific formats are the next step up.
How do I get faster at EV questions specifically?
Write each outcome × probability pair down before summing — most errors under time pressure come from pairing the wrong probability with the wrong outcome, not from the arithmetic itself. For "at least one" questions, computing the complement (nothing happens, at all) and subtracting from 1 is almost always faster than summing every individual success case directly.
Why is this separate from sequences now?
They're unrelated skills — probability/EV calculation versus pattern recognition in a series — bundled together in one legacy test only because they're both "generic firm-test" formats. This page is probability & EV only; see the separate Daily Sequence drill for number patterns.
Is there a longer, combined version?
Yes — the original 60-question Sequences & Probability test mixes both skills in one realistic-length fixed set. This daily drill is a shorter, probability-only, rotating alternative for regular practice.