McKinsey / Accenture / Got all BIG3 offers / More than 300 real MBB cases / Harvard Business School
Book a coaching

How Many Fish are in all the World’s Seas?

Riccardo

How would you structure your approach to solve that question ?

  • Upvotes
  • Date ascending
  • Date descending
Vlad replied on 02/16/2018
McKinsey / Accenture / Got all BIG3 offers / More than 300 real MBB cases / Harvard Business School

Hi,

I will use the following approach:

1) Take the Sea you know and try to calculate it's Volume. You may use the speed of a plain as the benchmark and assume that the Sea is 1/2 of a Sphere:

  • It takes X hours to fly from A to B over the Sea
  • The average speed of a plane is Z
  • Thus the radius of the Sea is 1/2 * X* (Z-1) (Because it takes extra hour to take off and land)
  • The volume of the sphere is 4/3 * p* rˆ3
  • The volume of the Sea is 1/2 * 4/3 * p * rˆ3 (Half of the sphere)

2) Make assumptions about the number of fish per 100 mˆ3

3) Calculate volume of fish in the Sea using your assumptions about the fish

4) Calculate the other seas using the assumption about their relative size

5) Sum up the numbers

Best

Juan Pablo replied on 02/15/2018

What they want to understand is what is your approach to that brainteaser. In this case i would suggest in a general perspective to do the following:

Start saying that in each KM3 there are x Number of Fish, then you can proceed by calculating the numer of fish in each ocean, having in mind that there are a lot of differences in the composition of the Atlantic´s ocean than the Dead sea.

Based on that, you should calculate the volume of each ocean and then making multiplying it by the number of fish in each of them. if you want to go further in your analysys, you could come up with the fish born seasonality, which could impress your interviewer but at the same time could mean much difficult calculations.

Hope it works.

Best,

Juan Pablo Montoya

Andrea
Expert
replied on 02/25/2018
Former BCG decision round interviewer with 300+ real interviews in 8 years

I would drastically simplify how to calculate the size of the sea by starting with assumption that there is a maximum sea depth that is compatible with most life, call it 30, 50, 100 meters. Once you agree on that you can approximate all seas to a composition of cuboids vs. spheres, making calculations faster and smoother. Once calculated the volume, apply assumed population per cubic kilometer and voila, done.

hope it helps,

andrea

Related BootCamp article(s)

Important Facts

It's essential to know some key figures regarding geographies, population, economies for your case interviews. We summarized them for you here.

9 Comment(s)

Market Sizing

Market Sizing Cases are used to test your quantitative and reasoning skills. The interviewer evaluates your structure, numbers-handling and business sense.

16 Comment(s)

Related case(s)

Your client, large automotive OEM WyCar, has developed its first fully electric vehicle (EV) and introduced it as a pilot on the Austrian market last year. However, sales have been far below the expected numbers. The management has engaged you to support them in understanding the reasons and advise ... Open whole case

Bain Case: Old Winery

Solved 10.8k times
4.4 5 287
| Rating: (4.4 / 5.0)

You have inherited the “Old Winery” from your grandfather, a winery which has been family owned for five generations and can be dated back to the 16th century. Half of the eleven hectares are used to grow white grapes, the other half to grow red grapes. They are grown in the conventional way, i.e ... Open whole case

Onlinestar, an online retailer of furniture and garden products (core business), has grown significantly in recent years as a result of an expansion of its product portfolio. The company mainly imports goods from Chinese manufacturers but also operates its own production of cat lavatories (special b ... Open whole case

Nutripremium

Solved 39.3k times
4.5 5 1149
| Rating: (4.5 / 5.0) |

Nutripremium is a very well-known premium nutrition food company in Europe (€1 billion revenue last year). It is based in Spain and has an excellent market share not only in its home country but also in Portugal, France, Italy and Germany. Nutripremium has two main lines of products: Vitam ... Open whole case

Children vaccine

Solved 36.2k times
4.4 5 1138
| Rating: (4.4 / 5.0) |

Beyer, one of the biggest pharmaceutical companies in the world, just invented a very reliable vaccine against Chickenpox, a disease that affects children in the age from 2 to 16 years. Beyer came to you wondering what their potential sales in Europe in the first year would be if they launched th ... Open whole case