Brain Teasers - Ping pong balls

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Calendar Cube

You are given two cubes with 6 sides each (total 12 sides). What digits would you put on each cube for you to be able to show all the days of the month with these two cubes?

Chopped Cube

You are given a large cube made up of small cubes. Each side of the large cube is as wide as ten small cubes. Can you calculate the number of small cubes that make up the outside of the large cube?

Exporting ping-pong balls

You are given a task of exporting ping-pong balls. How many ping pong balls do you think you can fit in a Boeing 747 airplane?


Brain Teasers are short questions with difficult logical or creative answers. They are a good way to test your analytical skills and capacity to think out of the box. These short questions also show the interviewer your ability to elaborate on difficult tasks from the real world. Each Brain Teaser is supposed to be solved by the interviewee in about 5-10 minutes.

If the interviewee gets stuck in a brain teaser (i.e. spends more than 10 minutes), propose to go on to the next one.


Detaillierte Lösung

Calendar Cube

Put 0,1,2,3, 4 and 5 on one and 0, 1, 2, 6, 7 and 8 on the other one. Digit 6 can be flipped over and used as digit 9.

Chopped Cube

  • It is given that each side of the large cube has 10 small cubes.
  • The large cube is composed of 10 small cubes in each dimension, so it is composed of 10*10*10 or 1000 small cubes in all
  • The number of small cubes that are on the inside is 8*8*8 = 512 cubes
  • Therefore 1000-512 = 488 small cubes make up the outside of the large cube

Exporting ping-pong balls

  • Let us calculate the volume of Boeing 747 airplane by approximating it to a cylinder of length 200 feet and diameter 20 feet
  • Volume of Boeing 747 would be pi*length*radius^2 = pi*200*100 = 20000ft³*pi
  • Assumption - the diameter of a ping-pong ball is 2 inch and 25% of the space is wasted
  • Volume of a ping-pong ball: 1.33*pi*radius^3 = 1.33*pi*1 = 1.33in²*pi
  • The units are differing, so we transform 20,000 ft³ into in³ (x2000)= 40m
  • Therefore, 75 % of 40,000,000pi/1.33pi or 22.5m balls can fit in a Boeing 747 airplane

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Beste Antwort bisher:
Ex BCG | MBB Specialist | #1 Expert for meetings done (1100+) and recommendation rate (100%)

Hi Anonymous, there may be several reasons for that; some of them, in order of frequency, are: Your structure is not complete enough – you are just using not MECE/ not complete structure... (mehr)

Hey, I am new to this too, but I think I have some ideas for your problem. Your approach looks good, but I think you have a mistake in how you time the trains. You say that there is one train e... (mehr)

Bisher beste Antwort von 3 Antworten:
Two years conulting experience, went through lots of interviews and coached several candidates to MBB offers

Hi, good question! Probably somewhat depending on your interviewer, but this is my view on it. In this situation it's important to try to showcase as mluch of your consulting skills as possible. Be... (mehr)

Bisher beste Antwort von 2 Antworten:
Specific coaching: company you are applying for; 1st or 2nd round; your professional background; ...

Hi, here's how I would approach it - Define the geographic area to be covered [the whole world? the U.S.? NYC? Manhattan?...for this example I'll use Manhattan] - Population living there [~ 1... (mehr)

Bisher beste Antwort von 3 Antworten:
McKinsey / Accenture / Got all BIG3 offers / More than 300 real MBB cases / Harvard Business School

Hi, First of all, I totally agree with Francesco on the process. You should always come back to the cases you've solved and reevaluate your structures. Secondly, I believe it's very much related... (mehr)

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