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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60-second preview — upgrade to Diamond for full sessions
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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Moelis & Co.
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Moelis & Co.
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Perella Weinberg
“Once I read through the BIWS learning guides, I really didn’t refer to them again. I didn’t even really run through the 400 question guide once I found IB Vine, which I heard about through one of my classmates. We even get a free subscription (like most business schools) to Wall Street Prep, and if I’m being completely honest, I never even logged in to WSP. IB Vine is pretty much the only tool I used (along with our club question bank & mock interviews with peers) and it was invaluable for recruiting.”
Cantor Fitzgerald
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Barclays
“Very accurate questions and all of the solutions are easy to follow. At least 10 of the questions I studied through this platform appeared in my Round 1 or Superday interviews.”
TD Securities
“THANK YOU SO MUCH IB VINE, I COULD NOT HAVE DONE THIS WITHOUT YOU, SERIOUSLY!!! IB Vine was the best website ever. I spent at least two hours on this daily (seriously) from October through I get my offer in February.”
Citadel
“I’m doing public equities this summer and next. I know the name is “IB Vine” but at the undergrad level a lot of the technicals across public equities are the same as investment banking. I recommend your software to all my friends!”
Piper Sandler
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Lazard
“This was the greatest tool ever. I genuinely enjoyed running through the technicals/behaviorals and it was very helpful!”
Houlihan Lokey
“IB Vine was the most helpful resource I had during recruiting. I will continue to promote it to other students at WashU and elsewhere.”
Jefferies
“Awesome product, helped me crush my technicals in my interviews and land a great role. Thank you, seriously was a huge help.”
Morgan Stanley
“Very helpful to get real-life questions unlike the 400 guide, especially for merger math. Built deeper understanding of key concepts.”
Houlihan Lokey
“Extremely helpful study tool that carried me through the recruitment process from start to end.”
Evercore
“You guys are doing great work over there with IB Vine. Absolute staple for interview prep.”
Rothschild
“IB Vine was incredibly helpful and I am forever thankful for all the help.”
RBC
“IB Mock was amazing - I used it for multiple hours. Also the flashcards and the lessons features on IB Vine were fantastic. Thank you!”
Dragoneer
“IB Vine is such a great platform, really impressive. There is so much value in this. The audio podcasts / mock interview library are pretty incredible.”
Moelis & Co.
“I loved IB Vine. I’m going into Private Capital Advisory (PCA); you have the lessons on there for PCA and that was actually a game changer. I went into those interviews and knew about the core PCA concepts like net asset value, primary fundraising vs. secondary advisory, etc. I swear I was on IB Vine like a few hours a day. The opportunity to have that learning section and go through the questions people submit and everything — there’s no better tool out there. I loved the guides/lessons. The user interface is amazing. The way you’ve simplified it is so spectacular — it’s just so much easier to digest. It’s fun to use too; I’d rather use IB Vine than scroll through a guide. To be honest, I think the product is perfect. I genuinely owe you a big thanks.”
Moelis & Co.
“IB Vine is a tool we really love to use in the club I’m a part of, and there’s really no other resource like it. You guys do a phenomenal job with the question bank. I recruited specifically for Energy banking, and IB Vine was my most used resource for generalist questions (which were about 50% of my interview questions; the rest being Energy-specific); the majority of such questions I saw in interviews were at least similar (if not the same) to the ones on IB Vine.”
Perella Weinberg
“Once I read through the BIWS learning guides, I really didn’t refer to them again. I didn’t even really run through the 400 question guide once I found IB Vine, which I heard about through one of my classmates. We even get a free subscription (like most business schools) to Wall Street Prep, and if I’m being completely honest, I never even logged in to WSP. IB Vine is pretty much the only tool I used (along with our club question bank & mock interviews with peers) and it was invaluable for recruiting.”
Cantor Fitzgerald
“What a platform, made such a huge difference. I did superdays at Evercore, PJT, M. Klein and Barclays among others from a non-target school and did not miss a single technical in any interview process through prepping with IB Vine.”
Barclays
“Very accurate questions and all of the solutions are easy to follow. At least 10 of the questions I studied through this platform appeared in my Round 1 or Superday interviews.”
TD Securities
“THANK YOU SO MUCH IB VINE, I COULD NOT HAVE DONE THIS WITHOUT YOU, SERIOUSLY!!! IB Vine was the best website ever. I spent at least two hours on this daily (seriously) from October through I get my offer in February.”
Citadel
“I’m doing public equities this summer and next. I know the name is “IB Vine” but at the undergrad level a lot of the technicals across public equities are the same as investment banking. I recommend your software to all my friends!”
Piper Sandler
“I loved this site! 1000% this is the best resource I used in the process.”
Lazard
“This was the greatest tool ever. I genuinely enjoyed running through the technicals/behaviorals and it was very helpful!”
Houlihan Lokey
“IB Vine was the most helpful resource I had during recruiting. I will continue to promote it to other students at WashU and elsewhere.”
Jefferies
“Awesome product, helped me crush my technicals in my interviews and land a great role. Thank you, seriously was a huge help.”
Morgan Stanley
“Very helpful to get real-life questions unlike the 400 guide, especially for merger math. Built deeper understanding of key concepts.”
Houlihan Lokey
“Extremely helpful study tool that carried me through the recruitment process from start to end.”
Evercore
“You guys are doing great work over there with IB Vine. Absolute staple for interview prep.”
Rothschild
“IB Vine was incredibly helpful and I am forever thankful for all the help.”
RBC
“IB Mock was amazing - I used it for multiple hours. Also the flashcards and the lessons features on IB Vine were fantastic. Thank you!”
Dragoneer
“IB Vine is such a great platform, really impressive. There is so much value in this. The audio podcasts / mock interview library are pretty incredible.”
Moelis & Co.
“I loved IB Vine. I’m going into Private Capital Advisory (PCA); you have the lessons on there for PCA and that was actually a game changer. I went into those interviews and knew about the core PCA concepts like net asset value, primary fundraising vs. secondary advisory, etc. I swear I was on IB Vine like a few hours a day. The opportunity to have that learning section and go through the questions people submit and everything — there’s no better tool out there. I loved the guides/lessons. The user interface is amazing. The way you’ve simplified it is so spectacular — it’s just so much easier to digest. It’s fun to use too; I’d rather use IB Vine than scroll through a guide. To be honest, I think the product is perfect. I genuinely owe you a big thanks.”
Moelis & Co.
“IB Vine is a tool we really love to use in the club I’m a part of, and there’s really no other resource like it. You guys do a phenomenal job with the question bank. I recruited specifically for Energy banking, and IB Vine was my most used resource for generalist questions (which were about 50% of my interview questions; the rest being Energy-specific); the majority of such questions I saw in interviews were at least similar (if not the same) to the ones on IB Vine.”
Perella Weinberg
“Once I read through the BIWS learning guides, I really didn’t refer to them again. I didn’t even really run through the 400 question guide once I found IB Vine, which I heard about through one of my classmates. We even get a free subscription (like most business schools) to Wall Street Prep, and if I’m being completely honest, I never even logged in to WSP. IB Vine is pretty much the only tool I used (along with our club question bank & mock interviews with peers) and it was invaluable for recruiting.”
Cantor Fitzgerald
“What a platform, made such a huge difference. I did superdays at Evercore, PJT, M. Klein and Barclays among others from a non-target school and did not miss a single technical in any interview process through prepping with IB Vine.”
Barclays
“Very accurate questions and all of the solutions are easy to follow. At least 10 of the questions I studied through this platform appeared in my Round 1 or Superday interviews.”
TD Securities
“THANK YOU SO MUCH IB VINE, I COULD NOT HAVE DONE THIS WITHOUT YOU, SERIOUSLY!!! IB Vine was the best website ever. I spent at least two hours on this daily (seriously) from October through I get my offer in February.”
Citadel
“I’m doing public equities this summer and next. I know the name is “IB Vine” but at the undergrad level a lot of the technicals across public equities are the same as investment banking. I recommend your software to all my friends!”
Piper Sandler
“I loved this site! 1000% this is the best resource I used in the process.”
Lazard
“This was the greatest tool ever. I genuinely enjoyed running through the technicals/behaviorals and it was very helpful!”
Houlihan Lokey
“IB Vine was the most helpful resource I had during recruiting. I will continue to promote it to other students at WashU and elsewhere.”
Jefferies
“Awesome product, helped me crush my technicals in my interviews and land a great role. Thank you, seriously was a huge help.”
Morgan Stanley
“Very helpful to get real-life questions unlike the 400 guide, especially for merger math. Built deeper understanding of key concepts.”
Houlihan Lokey
“Extremely helpful study tool that carried me through the recruitment process from start to end.”
Evercore
“You guys are doing great work over there with IB Vine. Absolute staple for interview prep.”
Rothschild
“IB Vine was incredibly helpful and I am forever thankful for all the help.”
RBC
“IB Mock was amazing - I used it for multiple hours. Also the flashcards and the lessons features on IB Vine were fantastic. Thank you!”
Dragoneer
“IB Vine is such a great platform, really impressive. There is so much value in this. The audio podcasts / mock interview library are pretty incredible.”
Moelis & Co.
“I loved IB Vine. I’m going into Private Capital Advisory (PCA); you have the lessons on there for PCA and that was actually a game changer. I went into those interviews and knew about the core PCA concepts like net asset value, primary fundraising vs. secondary advisory, etc. I swear I was on IB Vine like a few hours a day. The opportunity to have that learning section and go through the questions people submit and everything — there’s no better tool out there. I loved the guides/lessons. The user interface is amazing. The way you’ve simplified it is so spectacular — it’s just so much easier to digest. It’s fun to use too; I’d rather use IB Vine than scroll through a guide. To be honest, I think the product is perfect. I genuinely owe you a big thanks.”
Moelis & Co.
“IB Vine is a tool we really love to use in the club I’m a part of, and there’s really no other resource like it. You guys do a phenomenal job with the question bank. I recruited specifically for Energy banking, and IB Vine was my most used resource for generalist questions (which were about 50% of my interview questions; the rest being Energy-specific); the majority of such questions I saw in interviews were at least similar (if not the same) to the ones on IB Vine.”
Perella Weinberg
“Once I read through the BIWS learning guides, I really didn’t refer to them again. I didn’t even really run through the 400 question guide once I found IB Vine, which I heard about through one of my classmates. We even get a free subscription (like most business schools) to Wall Street Prep, and if I’m being completely honest, I never even logged in to WSP. IB Vine is pretty much the only tool I used (along with our club question bank & mock interviews with peers) and it was invaluable for recruiting.”
Cantor Fitzgerald
“What a platform, made such a huge difference. I did superdays at Evercore, PJT, M. Klein and Barclays among others from a non-target school and did not miss a single technical in any interview process through prepping with IB Vine.”
Barclays
“Very accurate questions and all of the solutions are easy to follow. At least 10 of the questions I studied through this platform appeared in my Round 1 or Superday interviews.”
TD Securities
“THANK YOU SO MUCH IB VINE, I COULD NOT HAVE DONE THIS WITHOUT YOU, SERIOUSLY!!! IB Vine was the best website ever. I spent at least two hours on this daily (seriously) from October through I get my offer in February.”
Citadel
“I’m doing public equities this summer and next. I know the name is “IB Vine” but at the undergrad level a lot of the technicals across public equities are the same as investment banking. I recommend your software to all my friends!”
Piper Sandler
“I loved this site! 1000% this is the best resource I used in the process.”
Lazard
“This was the greatest tool ever. I genuinely enjoyed running through the technicals/behaviorals and it was very helpful!”
Houlihan Lokey
“IB Vine was the most helpful resource I had during recruiting. I will continue to promote it to other students at WashU and elsewhere.”
Jefferies
“Awesome product, helped me crush my technicals in my interviews and land a great role. Thank you, seriously was a huge help.”
Morgan Stanley
“Very helpful to get real-life questions unlike the 400 guide, especially for merger math. Built deeper understanding of key concepts.”
Houlihan Lokey
“Extremely helpful study tool that carried me through the recruitment process from start to end.”
Evercore
“You guys are doing great work over there with IB Vine. Absolute staple for interview prep.”
Rothschild
“IB Vine was incredibly helpful and I am forever thankful for all the help.”
RBC
“IB Mock was amazing - I used it for multiple hours. Also the flashcards and the lessons features on IB Vine were fantastic. Thank you!”
Dragoneer
“IB Vine is such a great platform, really impressive. There is so much value in this. The audio podcasts / mock interview library are pretty incredible.”
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