How much paint need for....?

Question

Hi All,

How would you calculate the liters of paint needed to cover all the streets of a specific country or city?

I would approach it like this:

1) Start with the area of that country/city

2) Assume that 20% is covered by nature/ crops, 50% by buildings (residential and non residential) and 30% by roads (incl. small country roads, medium roads, high-ways and residential streets and avenues)

3) Multiply the total area*30% and the find the area covered by streets

4) Assuming that with 1L of paint you can cover 20 sq.mt, divide the area covered by streets by 20 sq. mt

5) At the end, I would include an additional 20% of paint (in case of painting obstacles ) and mention that it perhaps also depeneds by the quality/ material of the roads.

Does this seem fair? I am not sure about the assumptions I give at point No.2 - Are there any other approaches?

Thanks!

Answer 1

Hello,

I think your approach is fair as you cover the most important steps in these kinds of market sizing:
1. Start with Top-Down and slice the “market” into segments → Narrow down on the one you are interested in

2. Further break down your segment into different caregories: to go further you could've identified different needs for the categories of street you mentioned (e.g. high-way easy to paint, 1 layer, country road harder to paint, 2 layers)

3. Your assumption #4 is the right way to look at it - here as you don't know, selecting something that makes sense and is easy to calculate is the best approach (round numbers, easy to divide/multiply)

4. Very good to not stop at “the final number is X” but to include contingency / risks. You could also mention what additional data points you would want to validate to ensure that your approach is comprehensive.

==> Remember that the goal of these exercises is not to get to the right number, but to see how you think and approach a problem in a few minutes to get to a sensible answer.

Good job !
Happy to chat if you have questions, Cheers!

Answer 2

Hi there,

A few concerns:

Only 20% nature/farm is extremely small - even for a dense country! If it's a city, ok. Country, no
I can't imagine anywhere that has 30% of its entire landmass as roads only
Why 1L of paint? You need to break down this assumption (yellow side strip, white middle strip, width/length, and then how much paint)

There are some good things here but you've also missed the mark a bit in terms of your assumptions.

Here's some additional practice for you: https://www.preplounge.com/en/management-consulting-cases/brain-teaser/intermediate/taxis-in-manhattan-market-sizing-229

Answer 3

Hello!

Yes, your approach sounds about right! Don´t forget to ask questions along the way, since sometimes they do have hints about the percetages, etc.

Given that market sizing cases were the topic of many questions in this Forum, I developped a market sizing case, that you can find for free in PrepL´s library

https://www.preplounge.com/en/management-consulting-cases/candidate-led-usual-style/intermediate/market-sizing-new-startup-launch-baby-strollers-in-the-us-244

Let me know if you have any doubts with it, it contains a detailed explanation and methodology about how to solve this specific example, but you can extrapolate to many other market sizings!