What brainteasers has everyone been asked in interviews?

Ill go first:

1) What is 49 x 49?
2) If I have a cube which is 10x10x10, and I take off one layer. How many squares are left?
3) What is the sum of all numbers between 0-100?

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Comments (1109)

Jan 5, 2008 - 11:45am

1) 49^2 = (50-1)^2 = 2500-100+1 = 2401
2) 8^3 = 648 = 512
3) 100(101)/2= 50
101= 5050

(asked by a trader, and this is a serious brainteaser btw)

you have three guys, 1 girl, and two condoms. you all want to have heterosexual sex separately with her except you don't want to contract aids (meaning you never actually exchange fluids with either other men or the other woman). How is this possible?

Jan 5, 2008 - 11:49am

There was a pretty long brainteaser topic a few weeks ago. Over 80 responses. Here's a link.

- Capt K - "Prestige is like a powerful magnet that warps even your beliefs about what you enjoy. If you want to make ambitious people waste their time on errands, bait the hook with prestige." - Paul Graham
  • 1
Jan 5, 2008 - 11:40am

condom answer: first guy puts on both condoms (unsafe, buts its the only way to do it). second guy puts on the condom that was on top of the first guy when he wore two, because that inside has only touched the other condom. then the third guy turns the last condom inside out and uses that.

Jan 5, 2008 - 1:34pm
Grinder86:
condom answer: first guy puts on both condoms (unsafe, buts its the only way to do it). second guy puts on the condom that was on top of the first guy when he wore two, because that inside has only touched the other condom. then the third guy turns the last condom inside out and uses that.

lol....that's just terrible :( so much for sex ed these days

​* http://www.linkedin.com/in/numicareerconsulting
  • 1
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Jan 5, 2008 - 8:01pm

I can't believe you're actually asked a condom question. I've NEVER ever been asked any sexual questions during interviews. Prolly since I'm a girl. It's so ridiculous. The girl has three holes right? One can stick it in her pussy, one in the ass and one in the mouth. PRESTO! AIDS schmaids.

********"Babies don't cost money, they MAKE money." - Jerri Blank********

********"Babies don't cost money, they MAKE money." - Jerri Blank********
  • 1
Jan 6, 2008 - 12:01pm

well first guy uses 2 condoms = outside condom (condom 1) has girl fluids and inside condom (condom 2) has guy fluids

second guy uses condom 1 such that he has the unused part on himself and the girl on the side with her own fluids.

the last guy turns condom 2 inside out, puts the 2 condoms together such that the 1st and 2nd guy's fluids are together in the middle while he is wearing the fresh part with the girl fluids side of the condom on the outside again.

to summarize - 2 condoms as follows
girl/unused unused/guy 1
girl/guy 2
girl/guy 2 guy 1/ unused

presto.

Jan 6, 2008 - 12:03pm

Fun brain teasers - Part3 (Originally Posted: 05/08/2012)

An analyst, Associate, VP, and MD are walking home from their adventures in the jungle after a big M&A deal. They come to a bridge over a river at nightfall. The bridge is old and narrow and they decide that to ensure the bridge does not break, at most two people can be on the bridge at any given time. The have one source of light, an Iphone, and because it is night, the Iphone must be used when crossing the bridge. When two people are walking over the bridge, they move at the rate of the slower person. The MD can get across the bridge in 1 minute, the VP in 4, the Associate in 9 and the Analyst in 30. What is the fastest that everyone can get across the bridge?

Jan 6, 2008 - 12:05pm

So if I'm reading this correctly someone will have to walk the i-phone back after each crossing:

MD and analyst walk across in 30 min followed by the MD crossing the bridge in his lonesome = 31 min

MD and associate cross in 9 min with the MD walking back in 1 min = 10 min

MD and VP cross in 4 min = 4 min

Total = 45 minutes

Making money is art and working is art and good business is the best art - Andy Warhol
Best Response
Jan 6, 2008 - 12:06pm

MD and VP walk together = 4 minutes
MD returns back with iPhone = 1 minute
Associate and analyst walk = 30 mins
VP returns back with iphone and joins MD = 4 minutes
MD and VP walk and join Associate and analyst = 4 minutes

Total time = 43 mins

Jan 6, 2008 - 12:08pm
sb_guru:
MD and VP walk together = 4 minutes
MD returns back with iPhone = 1 minute
Associate and analyst walk = 30 mins
VP returns back with iphone and joins MD = 4 minutes
MD and VP walk and join Associate and analyst = 4 minutes

Total time = 43 mins

Win.

Jan 6, 2008 - 12:09pm
sb_guru:
MD and VP walk together = 4 minutes
MD returns back with iPhone = 1 minute
Associate and analyst walk = 30 mins
VP returns back with iphone and joins MD = 4 minutes
MD and VP walk and join Associate and analyst = 4 minutes

Total time = 43 mins


Credit given where credit is due. (What was I thinking?)
Making money is art and working is art and good business is the best art - Andy Warhol
Jan 6, 2008 - 12:16pm

MBPs brain teasers Part 4 (Originally Posted: 05/15/2012)

You are the ruler of a medieval empire and you are about to have a celebration tomorrow. The celebration is the most important party you have ever hosted. You've got 1000 bottles of wine you were planning to open for the celebration, but you find out that one of them is poisoned.

The poison exhibits no symptoms until death. Death occurs within ten to twenty hours after consuming even the minutest amount of poison.

You have over a thousand slaves at your disposal and just under 24 hours to determine which single bottle is poisoned.

You have a handful of prisoners about to be executed, and it would mar your celebration to have anyone else killed.

What is the smallest number of prisoners you must have to drink from the bottles to be absolutely sure to find the poisoned bottle within 24 hours?


SB to the first correct solution.

-MBP
  • 6
Jan 6, 2008 - 12:33pm

MBPs brain teasers Part 1 (Originally Posted: 05/08/2012)

A king has two sons of roughly the same age, intellect, compassion, political acumen etc., and on his death bed, cannot decide whom to leave the kingdom to. He devises an interesting competition, and summons the princes.


King: Sons, you will take your camels to the northern boundary of this kingdom and bring me the red jasmine, which only grows in one garden at the northern boundary. Whoever's camel is last to return will succeed me.

Upon hearing this, the princes mount their camels and ride for this garden at the northern kingdom. Once they arrive and each of them picks their red jasmine for their father, they are completely confused about what to do. They sit there waiting, thinking, for 3 days. Finally, the gardener, annoyed, asks them why they are lingering in his garden. They tell the gardener their paradox and he thinks to himself for a few minutes. After the pause, he gives them some advice. Upon hearing this advice, the princes mount the camels and race back to the kingdom as fast as they possibly can.

What advice did the gardener give them?


SB for the first correct response.

-MBP
  • 5
Jan 6, 2008 - 12:45pm

brain teaser question for you (Originally Posted: 08/13/2007)

how much would you pay to play this game?

a dice is thrown.
if its 1, 2 or 3, I put 1 pound in the pot, and the dice is thrown again.
if its 4 or 5, the game finishes, and you win whatever is in the pot.
if its 6, you leave with nothing.

Jan 6, 2008 - 12:59pm

Can someone please help me with this brain teaser? (Originally Posted: 10/01/2015)

I found this as one of the brain teasers asked during an interview. I cannot say whether this question is complete because the answer to me does not make sense so maybe it is missing some information. I would really appreciate it if someone could help me out with the solution and the logic behind it as I have an interview with this bank next week:

If bus tokens cost $1.5 today and $2 tomorrow, how many would you buy? Your required rate of return is 10% and give your answers in time.

Jan 6, 2008 - 1:39pm

MBPs brain teasers Part 3 (Originally Posted: 05/14/2012)

A group of 7 pirates discover a chest of 7000 gold coins. The 7 pirates are ranked from highest (captain) to lowest (deck cleaner). There are no equal ranks. Each of the 7 pirates is very smart, rational, and selfish.

The captain proposes the distribution of the 7000 coins. If he gets at least half the votes (including his own vote), the distribution stands. If not, there is a mutiny and the captain is killed, and the next highest ranked officer assumes the captain role and proposes a new distribution.

If you were the captain, what distribution would you propose?

As always, SB for the first correct answer with correct thought process.

-MBP
  • 3
Jan 6, 2008 - 1:57pm

MBPs brain teasers Part 2 (Originally Posted: 05/08/2012)

Since the first one was really easy, here's one that should get a bit more discussion/

Once again, first correct answer gets an SB.

Note: this is a simplification of the mother of all brain teasers.


There are three gods. Liar, who always lies, Honest, who always tells the truth, and Random, who lies or tells the truth depending on his mood.

When Random decides to lie, if asked about his own identity, he will always say that he is Honest, and if asked about another, he will never say the other is Random.

When Liar lies about his own identity, he pretends to be Honest. When he lies about another, he says the other is Liar.

These three gods grant a wish if someone is able to determine their identities. The rule is that only three questions can be asked (one each). If based on these three questions, the human can determine the three identities, he gets his wish. If he can't, the gods eat him.

The three gods stand next to one another in a line while the human asks his questions. Also, the gods are aware of each others identities.

What three questions should the human ask, and demonstrate how the questions will reveal the identities of the gods.

-MBP
  • 5
Jan 6, 2008 - 2:21pm

Fun brain teasers - Part1 (Originally Posted: 05/07/2012)

I love Math, Logic Games, and Puzzles. Here is the first installment. I will start with relatively simple ones, and will make them progressively harder as people answer them correctly.

What is the largest number possible only using two digits? No operations or symbols, only digits.

Jan 6, 2008 - 2:33pm

Is it just 3 or am I missing something?

Grab one sock, white or black, put it aside.

Grab another sock, possibly the other color.

If you grab a third no matter what you're going to have a pair.

"The only point in making money is so you can tell some big shot where to go.” -Bogie
Jan 6, 2008 - 2:35pm
MSFhopeful:
Is it just 3 or am I missing something?

Grab one sock, white or black, put it aside.

Grab another sock, possibly the other color.

If you grab a third no matter what you're going to have a pair.


Yeah.
-MBP
Jan 6, 2008 - 2:42pm

Is it not 2? Two is a pair?

I hate victims who respect their executioners
Jan 6, 2008 - 2:53pm

Brainteaser - Technical brainteasers? (Originally Posted: 07/30/2012)

What are some of the brain teasers you guys have been asked thus far? Let's try to get a good collection together here, should help everyone in their interview efforts.

I'm talking about liquid. Rich enough to have your own jet. Rich enough not to waste time. Fifty, a hundred million dollars, buddy. A player. Or nothing.

See my Blog & AMA

Jan 6, 2008 - 2:54pm

The hardest brainteaser I ever got was a riddle:

It starts with the letter "S".
It's two words.
It's on every forum.
It rhymes with the phrase "Church Glutton".

S _ AR _ H
B_ _ _ ON

Solve the puzzle.

Robert Clayton Dean: What is happening?
Brill: I blew up the building.
Robert Clayton Dean: Why?
Brill: Because you made a phone call.

  • 4
Jan 6, 2008 - 3:07pm

Interview Logic Riddles and Brainteasers (Originally Posted: 03/23/2017)

In investment banking interviews, it is common for interviewers to ask questions to test your critical / creative thinking skills under pressure. The OP shared some common questions asked by interviewers below.

investment banking brain teasers

  1. What is the largest possible number you can write using only 2 numbers - just 2 numbers, no other mathematical symbols?
  2. If, having only one match, on a freezing winter day, you entered a room which contained a lamp, a kerosene heater, and a wood burning stove, which should you light first.
  3. What belongs to you, but is mostly used by others?
  4. How many birth days does the average man have?
  5. Two planes take off at the same exact moment. They are flying across the Atlantic. One leaves New York and is flying to Paris at 500 miles per hour. The other leaves Paris and is flying to New York at only 450 miles per hour ( because of a strong head wind ). Which one will be closer to Paris when they meet?
  6. A 10 foot rope ladder whose rungs are one foot wide is hanging over the side of a boat. At this time there is only 1 foot of ladder under the water. It now begins to rain heavily, if it rains at the rate of 1 foot every two hours, how many hours will it take to cover half of the ladder?

As simple as these may sound, a lot of people struggle with these in investment banking interviews.

How to Answer Consulting Brainteasers

Brainteasers are common in both investment banking and consulting interviews. Check out a video below discussing how to answer consulting interview questions.

Throwback Thursday, this was originally posted almost 9 years ago! 4/13/08

Read More About Brainteasers on WSO

Preparing for Investment Banking Interviews?

The WSO investment banking interview course is designed by countless professionals with real world experience, tailored to people aspiring to break into the industry. This guide will help you learn how to answer these questions and many, many more.

Investment Banking Interview Course Here

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Jan 6, 2008 - 3:11pm

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-------------------- "It is a fine thing to be out on the hills alone. A man can hardly be a beast or a fool alone on a great mountain." - Francis Kilvert (1840-1879) "Ce serait bien plus beau si je pouvais le dire à quelqu'un." - Samivel
Jan 6, 2008 - 3:13pm

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-------------------- "It is a fine thing to be out on the hills alone. A man can hardly be a beast or a fool alone on a great mountain." - Francis Kilvert (1840-1879) "Ce serait bien plus beau si je pouvais le dire à quelqu'un." - Samivel
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