Probability & EV Practice
Dice, coin and card probability plus expected-value calculation. Today's free drill comes from a 180-day pool. No signup. Runs 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. Everyone gets the same 15 questions today.
0.25 or 1/4).Six probability question types
Each type comes up again in the brain-teaser and market-making rounds later in the interview process:
| 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 has 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) is easiest via the complement: 1 − (5/6)⁴ ≈ 0.52. |
Probability and EV in later interview rounds
Interviewers use the same probability and EV tools in brain-teaser rounds, and EV explains why negative marking changes test strategy. The full prep guide covers both in more depth. The Robot Games drill applies the same EV-sign judgment to a timed Play/Pass decision instead of a typed number.
Number sequence practice
Sequences have their own daily drill: Number Sequence Practice. For both skills in one test, take the 60-question Sequences & Probability test.
Related practice
- Robot Games: timed Play/Pass EV decisions
- Quant interview brain teasers: worked probability & EV puzzles
- How to prepare for a quant trading interview: the full pipeline and a study plan
Questions
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 reasonable target. This is a daily practice drill, so there is no firm cutoff or official pass mark. Once you score above that consistently, move on to the app's full-length firm formats.
How do I get faster at EV questions specifically?
Write down each outcome × probability pair before summing. Under time pressure, most errors come from pairing an outcome with the wrong probability rather than from the arithmetic. For "at least one" questions, compute the complement (nothing happens at all) and subtract it from 1. That is almost always faster than adding up every success case.
Why is this separate from sequences now?
They are different skills: probability and EV calculation, and pattern recognition in a series. An older test combined them only because both are generic firm-test formats. This page covers probability and EV only. Number patterns have their own Daily Sequence drill.
Is there a longer, combined version?
Yes. The original 60-question Sequences & Probability test mixes both skills in one full-length fixed set. This daily drill is shorter, covers probability only and rotates every day.