How long is the Quant Interview Brainteasers practice sitting?

Outcry’s mock has 36 items across 3 sections, with 90 minutes of section time. Those figures describe this mock; see the source check for any published format elements.

Will Quant Interview Brainteasers use the same questions every time?

Outcry generates questions from its own banks. Counts and rules remain fixed; the selected problem types or numeric parameters change. Some archetypes may recur across attempts.

Quant brainteasers · Technical skills · probability & logic

Quant Interview Brainteasers - Timed Practice

Outcry’s probability, reasoning and mathematical puzzle practice: 36 generated questions across three sections in 90 minutes. This is general interview-skills preparation, not a specific firm’s puzzle round.

Format

3 sections · 36 items · about 90 minutes
Format and scoring below apply to this Outcry mock. See the source check for verified firm details and practice adaptations.
Marking on Probability, Reasoning, Math: +1 correct, 0 wrong, 0 for a skip. Any item-specific mark weight is shown on the question.
No going back in this mock. Answer or skip, and the next item loads.
Questions are generated from Outcry's own banks; a retake changes the selection or parameters.

Sections

Probability - 14 items, 35 minutes, no negative marking. 14 items in 35 minutes. Linearity of expectation, Bayes, hypergeometric draws, gambler's ruin, coupon collector, optional stopping, waiting times.
Reasoning - 10 items, 30 minutes, no negative marking. 10 items in 30 minutes. Knights and knaves, hat deductions, weighings, constraint grids, parity and pigeonhole arguments, two-player games.
Math - 12 items, 25 minutes, no negative marking. 12 items in 25 minutes. Painted cubes, digit counting, trailing zeros, clock hands, lattice paths, tilings, modular arithmetic, geometric probability.

What this practice sitting covers

3 sections, 36 items and 90 minutes of section time. Each section uses its own clock. Questions are generated from Outcry’s own banks; repeat attempts can share problem types with different selections or parameters.

How this mock is marked

Marking on Probability, Reasoning, Math: +1 correct, 0 wrong, 0 for a skip. Any item-specific mark weight is shown on the question.

This mock has no back navigation: each submitted or skipped question is final.

Scores measure performance on these exercises. They are not a firm’s pass threshold or a prediction of an interview or offer.

Public sources and practice adaptations

Public trading interview resources demonstrate probability and mathematical problem-solving topics. No universal employer brainteaser paper is established.

The 36-question, 90-minute paper and all marking are Outcry settings. Individual firm attribution of a puzzle type is not a promise that it will appear.

Section by section, with a worked example

Every example below is generated by Outcry, drawn from the same generator that section runs during the timed sitting. None of it is any firm's own material.

A. Probability

14 items in 35 minutes. Linearity of expectation, Bayes, hypergeometric draws, gambler's ruin, coupon collector, optional stopping, waiting times.

In this Outcry section: 14 items in 35 minutes, averaging 150 seconds per item. Wrong answers receive no marks and carry no deduction. Unanswered items score zero. Correct-answer weights are shown on the questions. These are the mock’s rules.

Example 1

A counter sits on square 2 of a row numbered 0 to 12. Each tick it moves one square left or one square right with equal probability, and it stops on 0 or on 12. What is the probability it stops on 12?

Answer 1/6

The position itself is a martingale in a fair walk, so its expected stopping value equals its start: p x 12 + (1 - p) x 0 = 2, giving p = 2/12 = 1/6. Step size does not enter it.

Example 2

You start with 3 chips and stake one chip at a time on a bet you win with probability 55%. You stop at 6 chips or at 0. What is the probability you reach 6?

Answer 0.646

Gambler's ruin with a drift. Write r = q/p = 0.818. Then P = (1 - r^3)/(1 - r^6) = (1 - 0.548)/(1 - 0.3) = 0.646. The fair-game answer 1/2 is what you get only when r = 1.

B. Reasoning

10 items in 30 minutes. Knights and knaves, hat deductions, weighings, constraint grids, parity and pigeonhole arguments, two-player games.

In this Outcry section: 10 items in 30 minutes, averaging 180 seconds per item. Wrong answers receive no marks and carry no deduction. Unanswered items score zero. Correct-answer weights are shown on the questions. These are the mock’s rules.

Example 1

4 crates arrive at a receiving dock holding spacers, shims, gaskets and bolts, one content each. Each crate carries a label naming one of those 4 contents, no two labels the same, and every label is on the wrong crate. Opening a crate shows what is in it. How many crates must be opened, in the worst case, to relabel all 4 correctly?

Answer 2

The label-to-contents map is a permutation with no fixed point, and there are 9 of those on 4 items. Opening a crate reveals its contents and splits the live set; picking the next crate after seeing the last result, a minimax search over every opening order gives 2 as the worst case. With 4 = 3 the two possible arrangements are the two rotations, and one look separates them. The general pattern: the last two crates settle themselves only when the two contents left both clash with their own labels.

Example 2

Plate  12  19
Weld   12  14  17
Trim   15  16
Kiln   14  16  19

Ana: "I do not know which job it is, and I can tell that Ben does not know either."
Ben: "I did not know it before, but I do now."
Ana: "Then I know it too."

One maintenance job is booked. The list above gives every possibility as a workshop and a slot number. Ana is told the workshop only. Ben is told the slot only. Both know the list and both hear each other. Which job is it?

Plate, slot 12
Kiln, slot 19
Kiln, slot 14
Kiln, slot 16

Answer Plate, slot 12

Work the statements as filters over the 10 listed jobs. Ana knowing Ben cannot know means every slot in Ana's workshop appears at least twice on the list, which leaves 5: Plate, slot 12; Plate, slot 19; Kiln, slot 14; Kiln, slot 16; Kiln, slot 19. Ben then knows, so his slot is unique among those 5, leaving 3: Plate, slot 12; Kiln, slot 14; Kiln, slot 16. Ana then knows, so her workshop is unique among those, leaving Plate, slot 12. Each statement is information about what the speaker could rule out, not about the job itself.

C. Math

12 items in 25 minutes. Painted cubes, digit counting, trailing zeros, clock hands, lattice paths, tilings, modular arithmetic, geometric probability.

In this Outcry section: 12 items in 25 minutes, averaging 125 seconds per item. Wrong answers receive no marks and carry no deduction. Unanswered items score zero. Correct-answer weights are shown on the questions. These are the mock’s rules.

Example 1

A solid cube 7 by 7 by 7 is painted on all six outer faces, then cut into 343 unit cubes. How many of the small cubes have exactly 3 painted faces?

Answer 8

Sort the small cubes by position. Corners have 3 painted faces, edges 2, face middles 1, and the core 0. The 3-face group is the 8 corners, a count that does not move when 7 does. Check the total: 8 + 60 + 150 + 125 = 343.

Example 2

A courier travels 5 blocks east and 5 blocks north on a grid, moving only east or north, and has to collect a package at the corner 2 east and 2 north of the start. How many routes do that?

Answer 120

A route through a fixed point is two independent routes joined end to end. To the package: C(4,2) = 6. From there on: C(6,3) = 20. Multiply: 120.

Common questions

How long is the Quant Interview Brainteasers practice sitting?: Outcry’s mock has 36 items across 3 sections, with 90 minutes of section time. Those figures describe this mock; see the source check for any published format elements.
How does scoring work in Quant Interview Brainteasers?: Marking on Probability, Reasoning, Math: +1 correct, 0 wrong, 0 for a skip. Any item-specific mark weight is shown on the question.
Can I go back in Quant Interview Brainteasers?: This mock has no back navigation: each submitted or skipped question is final.
Will Quant Interview Brainteasers use the same questions every time?: Outcry generates questions from its own banks. Counts and rules remain fixed; the selected problem types or numeric parameters change. Some archetypes may recur across attempts.
Is Quant Interview Brainteasers an official assessment?: No. This is Outcry practice with original generated questions. The 36-question, 90-minute paper and all marking are Outcry settings. Individual firm attribution of a puzzle type is not a promise that it will appear.

Jane Street Probability & Markets

This is an Outcry skills mock, not a named employer’s assessment. Outcry is not affiliated with any firm and generates its own questions.