Case

Brain Teasers - Ping pong balls

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Problemdefinition

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?


Kommentare

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:
#1 Expert for coaching sessions (1500+) | Ex BCG | 650+ reviews with 100% recommendation rate

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)

Beste Antwort bisher:
McKinsey Engagement Manager & BCG Consultant | Interviewer at McK & BCG for 7 years | Coached 45+ candidates secure MBB offers

Hi Anonymous, first of all - this is not a brain teaaser, but an ordinary estimation question! Here is a high-level approach: I would start with the second question, because it is most straight forw... (mehr)

Bisher beste Antwort von 3 Antworten:
Sibren
Experte
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 3 Antworten:
An
Experte
Uber Strategy Manager | BCG Consultant, Interviewer

Hey there Here is one approach: # Hair Salons = (# hours required for men's haircuts per year + # hours required for women's haircuts per year) / average service capacity of 1 hair salon (which... (mehr)

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