General Brain Teasers — Investment Banking Mock Interview
Sharpen your mental math speed, market sizing frameworks, probability reasoning, and logic puzzle techniques with real IB-style questions.
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Key Topics Covered
Rapid-Fire Mental Math
Covers multiplication shortcuts like difference of squares and the (a+b) expansion, large-number squaring, decimal division tricks, square root approximation, percentage decomposition, and the sum of integers formula. The advanced session escalates to four-digit multiplication and chained calculations.
Market Sizing & Estimation
Walks through structured top-down estimation for Starbucks store revenue, the number of US gas stations, campus windows, NYC flu cases, Minneapolis sweater sales, US chewing gum market size, and bumblebee daily travel distance, demonstrating the population-times-frequency-times-price framework.
Logic Puzzles & Lateral Thinking
Covers the lily pad doubling problem in multiple variants, the five-gallon and three-gallon bucket measurement puzzle, the elevator riddle, and the nine-ball weighing problem, testing your ability to reason backwards and eliminate possibilities systematically.
Probability & Combinatorics
Includes the missile hit probability using complementary counting, the marble bowl optimization problem for maximizing draw probability, handshake counting with combinations, letter arrangement with constraints from the word ABACUS, and dice expected value with and without re-roll options.
Clock Angles & Spatial Reasoning
Calculates the angle between clock hands at 12:15, 3:15, and 1:43 using the degrees-per-minute framework. Also covers counting all squares on a chessboard and determining unpainted interior cubes in a 10x10x10 painted cube.
How to Prepare for General Brain Teasers Interviews
Practice mental math for 10 to 15 minutes daily using real numbers rather than cramming before an interview. Master the difference-of-squares shortcut (a-b)(a+b) = a^2 - b^2 for multiplying numbers equidistant from a round number, and the (a+b)^2 expansion for squaring numbers near 1000. These two tricks alone cover most mental math questions in these recordings.
For market sizing questions, always start by stating your top-level assumption (usually US population or a relevant subset), then walk through each step of the multiplication chain out loud. Interviewers care more about your structured decomposition and reasonableness checks than getting the exact number right.
Drill probability problems using the complement method: calculate the chance that nothing happens and subtract from one. The missile and marble bowl problems in these sessions both hinge on this technique, and it is by far the most common probability framework tested in IB interviews.
When facing an unfamiliar logic puzzle, resist the urge to guess immediately. Narrate your thought process aloud, write down what you know, and look for patterns or ways to work backwards from the answer. Interviewers evaluate your reasoning approach as much as the final answer, and staying calm under pressure is itself a signal they are testing for.
More Core Concepts Topics
View allAccounting
Covers foundational accounting concepts commonly tested in investment banking interviews. Discusses key definitions, frameworks, and walk-through questions at an introductory level.
Enterprise & Equity Value
Covers foundational enterprise & equity value concepts commonly tested in investment banking interviews. Discusses key definitions, frameworks, and walk-through questions at an introductory level.
Discounted Cash Flow (DCF)
Covers foundational dcf concepts commonly tested in investment banking interviews. Discusses key definitions, frameworks, and walk-through questions at an introductory level.
Valuation
Covers foundational valuation concepts commonly tested in investment banking interviews. Discusses key definitions, frameworks, and walk-through questions at an introductory level.
Leveraged Buyouts (LBO)
Covers foundational leveraged buyouts (lbos) concepts commonly tested in investment banking interviews. Discusses key definitions, frameworks, and walk-through questions at an introductory level.
Mergers & Acquisitions (M&A)
Covers foundational merger model (m&a) concepts commonly tested in investment banking interviews. Discusses key definitions, frameworks, and walk-through questions at an introductory level.
About This General Brain Teasers Mock Interview
These sessions cover rapid-fire mental math (multi-digit multiplication, square roots, percentage calculations, large-number squaring), classic logic puzzles (lily pad doubling, water bucket measurement, elevator riddle, nine-ball weighing), probability problems (missile hit probability, marble bowl optimization), clock angle calculations at multiple times, combinatorics, pattern recognition in number sequences, and a wide range of market sizing estimations including Starbucks revenue, US gas stations, university windows, flu cases, sweater sales, chewing gum market size, bumblebee travel distance, and monetizing 100 square miles of water.
This topic is part of the Core Concepts section of our investment banking mock interview library. It includes 2 sessions covering both basic and advanced difficulty levels. Each session includes multi-speaker audio with realistic interviewer questions and candidate responses, plus a full interactive transcript you can follow along with or study independently.
Audio Recording
28 minutes of multi-speaker audio
Full Transcript
Interactive transcript with timestamps
1 Basic + 1 Advanced
Basic & Advanced
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Analyst
I found this website really helpful, which also helps me better prepare for the technical interview in IBD position and get an offer.
Seen on WallStreetOasis
Check out IB Vine, specifically the 'IB Vine Select' questions. Once you can get a handle of those, it seems like you are in a spot where you're applying the concepts rather than simply memorizing them
Analyst
I've used IB Vine for my recruitment, and I could not imagine the journey without it. Thank you for creating a phenomenal resource.
Seen on WallStreetOasis
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Seen on WallStreetOasis
IB Vine has excellent questions, especially multistep ones. In my experience I've gotten grilled on accretion/dilution, bond math, and merger model questions. IB Vine has great practice for all of those.
User Story
As a nontraditional transfer student who has been rendered unavailable to many resources at my university (Leadership positions at clubs, immediately behind the recruiting cycle, etc.) IB Vine has been an absolute game changer in my IB prep.
Seen on WallStreetOasis
From my experience interviewing FT for IB, it’s not enough to just know the 400 questions anymore (it’s a good starting point) but to look at even more advanced questions. Would recommend IB Vine.
Seen on Twitter
heard all the new kids use IB Vine now. the questions on IB Vine helped me get the concepts down when I had to recruit and make a lot of BB/MM interviews easier than I expected for techs
User Story
Just got off the phone with a kid who interned at a Dallas PE firm. He mentioned that IB Vine helped him secure that internship as well as his Summer Analyst offer, especially since he came from a non-target with no resources.
Analyst
The IB Vine technical prep is beyond helpful, it's so much more fun quizzing myself every now and then vs. reading through the guides again.
Analyst
I personally found that the 'IB Vine Select' collection had some of the exact questions I was asked in my Qatalyst interviews.
Analyst
Thanks for starting up IB Vine. Couldn't have landed my offer without your help!
User Story
I honestly think you're doing gods work since IB Vine democratizes the whole interview process and helps a lot of students ace their interviews.
Analyst
I found this website really helpful, which also helps me better prepare for the technical interview in IBD position and get an offer.
Seen on WallStreetOasis
Check out IB Vine, specifically the 'IB Vine Select' questions. Once you can get a handle of those, it seems like you are in a spot where you're applying the concepts rather than simply memorizing them
Analyst
I've used IB Vine for my recruitment, and I could not imagine the journey without it. Thank you for creating a phenomenal resource.
Seen on WallStreetOasis
Beyond the 400 questions guide, try to understand a deeper level and the underlying concepts of the questions being asked. Use ibvine, it really helps.
Seen on WallStreetOasis
IB Vine has excellent questions, especially multistep ones. In my experience I've gotten grilled on accretion/dilution, bond math, and merger model questions. IB Vine has great practice for all of those.
User Story
As a nontraditional transfer student who has been rendered unavailable to many resources at my university (Leadership positions at clubs, immediately behind the recruiting cycle, etc.) IB Vine has been an absolute game changer in my IB prep.
Seen on WallStreetOasis
From my experience interviewing FT for IB, it’s not enough to just know the 400 questions anymore (it’s a good starting point) but to look at even more advanced questions. Would recommend IB Vine.
Seen on Twitter
heard all the new kids use IB Vine now. the questions on IB Vine helped me get the concepts down when I had to recruit and make a lot of BB/MM interviews easier than I expected for techs
User Story
Just got off the phone with a kid who interned at a Dallas PE firm. He mentioned that IB Vine helped him secure that internship as well as his Summer Analyst offer, especially since he came from a non-target with no resources.
Analyst
The IB Vine technical prep is beyond helpful, it's so much more fun quizzing myself every now and then vs. reading through the guides again.
Analyst
I personally found that the 'IB Vine Select' collection had some of the exact questions I was asked in my Qatalyst interviews.
Analyst
Thanks for starting up IB Vine. Couldn't have landed my offer without your help!
User Story
I honestly think you're doing gods work since IB Vine democratizes the whole interview process and helps a lot of students ace their interviews.
Analyst
I found this website really helpful, which also helps me better prepare for the technical interview in IBD position and get an offer.
Seen on WallStreetOasis
Check out IB Vine, specifically the 'IB Vine Select' questions. Once you can get a handle of those, it seems like you are in a spot where you're applying the concepts rather than simply memorizing them
Analyst
I've used IB Vine for my recruitment, and I could not imagine the journey without it. Thank you for creating a phenomenal resource.
Seen on WallStreetOasis
Beyond the 400 questions guide, try to understand a deeper level and the underlying concepts of the questions being asked. Use ibvine, it really helps.
Seen on WallStreetOasis
IB Vine has excellent questions, especially multistep ones. In my experience I've gotten grilled on accretion/dilution, bond math, and merger model questions. IB Vine has great practice for all of those.
User Story
As a nontraditional transfer student who has been rendered unavailable to many resources at my university (Leadership positions at clubs, immediately behind the recruiting cycle, etc.) IB Vine has been an absolute game changer in my IB prep.
Seen on WallStreetOasis
From my experience interviewing FT for IB, it’s not enough to just know the 400 questions anymore (it’s a good starting point) but to look at even more advanced questions. Would recommend IB Vine.
Seen on Twitter
heard all the new kids use IB Vine now. the questions on IB Vine helped me get the concepts down when I had to recruit and make a lot of BB/MM interviews easier than I expected for techs
User Story
Just got off the phone with a kid who interned at a Dallas PE firm. He mentioned that IB Vine helped him secure that internship as well as his Summer Analyst offer, especially since he came from a non-target with no resources.
Analyst
The IB Vine technical prep is beyond helpful, it's so much more fun quizzing myself every now and then vs. reading through the guides again.
Analyst
I personally found that the 'IB Vine Select' collection had some of the exact questions I was asked in my Qatalyst interviews.
Analyst
Thanks for starting up IB Vine. Couldn't have landed my offer without your help!
User Story
I honestly think you're doing gods work since IB Vine democratizes the whole interview process and helps a lot of students ace their interviews.
Analyst
I found this website really helpful, which also helps me better prepare for the technical interview in IBD position and get an offer.
Seen on WallStreetOasis
Check out IB Vine, specifically the 'IB Vine Select' questions. Once you can get a handle of those, it seems like you are in a spot where you're applying the concepts rather than simply memorizing them
Analyst
I've used IB Vine for my recruitment, and I could not imagine the journey without it. Thank you for creating a phenomenal resource.
Seen on WallStreetOasis
Beyond the 400 questions guide, try to understand a deeper level and the underlying concepts of the questions being asked. Use ibvine, it really helps.
Seen on WallStreetOasis
IB Vine has excellent questions, especially multistep ones. In my experience I've gotten grilled on accretion/dilution, bond math, and merger model questions. IB Vine has great practice for all of those.
User Story
As a nontraditional transfer student who has been rendered unavailable to many resources at my university (Leadership positions at clubs, immediately behind the recruiting cycle, etc.) IB Vine has been an absolute game changer in my IB prep.
Seen on WallStreetOasis
From my experience interviewing FT for IB, it’s not enough to just know the 400 questions anymore (it’s a good starting point) but to look at even more advanced questions. Would recommend IB Vine.
Seen on Twitter
heard all the new kids use IB Vine now. the questions on IB Vine helped me get the concepts down when I had to recruit and make a lot of BB/MM interviews easier than I expected for techs
User Story
Just got off the phone with a kid who interned at a Dallas PE firm. He mentioned that IB Vine helped him secure that internship as well as his Summer Analyst offer, especially since he came from a non-target with no resources.
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