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How much water is needed for one cup of coffee?

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New answer on Mar 09, 2023
4 Answers
Anonymous A asked on Mar 08, 2023


I have encountered such types of questions. How to work with them? I guess it's all about the whole process, however, I'm not sure that I'm making a right structure. Can you please help me? 

My idea now is to break it into several steps (to grow, to process the berries, to roast the beans, to pack them and finally to sell and make a cup of coffee). However, I got completely lost, while trying to figure the proper structure for each stage) 

Thank you!

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replied on Mar 08, 2023
PL-level BCG experience (6 years)|Interviewer at BCG| 6/6 personal + 95%+ candidates offer success rate

HI there,

1) Make sure you are solving the right case i.e. clarfy upfront. Confirm the real case ask is  

a) How much water is needed to produce a cup “worth” of coffee?

b) Confirm if there are any boundaries to this analysis (e.g. process wise)

2) Potential approach

a) Agree with the process split up in 2-3 step maximum: a1) cultivation a2) treatment and fermeting b) brewing c) transporting, …

b) Let us first assess how much coffee is needed for one cup (e.g. 10g) 

c) For each step let us imagine / describe the process + try to further narrow down on scope and variable impacting the water consumption (e.g. what type of production method - dry vs. wet, what type of geo we are talking about, is natural rainfall involved - should I count this in my sizing?, what type of soil, is this a concious producer saving water, ….)  

d) Probe interviewer for typical benchmark “ratios": e.g. m3 water/ton for each process stage BUT only after having explained the logical variables as per above

e) painful alternative - only if 1 not successful. Let us use the right "scaling" and common sense - If I were to think about my backyard garden 1m x 1m - how much water would I pour in (e.g. litres over time) to make a plant grow there (e.g. along xx days I would water them x times every z days, …) and then try to assess how many coffee grams I can extract from this single m2 of backyard to obtain a m3 water/g ratio out of thinking 

 Bottom line

1) Segment process - probe for ratios; if not successful painful “common experience” bottom down proxies


Hope this helps


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Content Creator
replied on Mar 09, 2023
#1 recommended coach | >95% success rate | most experience in consulting, interviewing, and coaching

Hi there,

I think this is an interesting question that may be relevant for many people. I would be happy to share my thoughts on it:

  • First of all, while this type of brain teaser/mini case might still occur with smaller strategy consulting companies, it is generally very rare and will not happen with any bigger strategy consulting company for the simple reason that they are very limited with regards to the skills and the scope of how these skills are being tested.
  • Moreover, I like your approach, and most likely, I would have approached it the same way by analyzing the value chain and identifying the amount of water required for each "product" created at each step. Unfortunately, the value chain and some details are all that can be provided for the structure (once again, it highlights that the scope of skills being tested is limited).

If you would like a more detailed discussion on how to address your specific situation, please don't hesitate to contact me directly.



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Content Creator
replied on Mar 09, 2023
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

Hi there,

I like how you have broken down the process. I also like how Paul has pointed out how important it is to clarify the question so that you are sure about what you are solving for.

This is basically a market sizing, so all the same market sizing rules apply here!

The most important one for you right now? Leverage what you know about the world to estimate, not guess. Break down the problem into segments that allow you to estimate based on what you know already.

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replied on Mar 09, 2023
Bain | EY-Parthenon | Private Equity | Market Estimates | Fit Interview

You are on the right track. Basically define the process. Then you have to consider IF and WHY you need water in that process step. Then how much you need.

Usually you will need significant ammount of water to grow the beans and to make the coffee.

What are you missing? 

- First you are not closing the loop, i.e., the process does not stop when the cup is served (you need to wash the cup later on… or if you prefer, before you pour the coffee).

- Second there are a lot of associated processes / goods (cleaning the coffee shop, water in energy production, etc. etc). Although I feel one could fall into a rabit's hole going down this path. I would just state this and dismiss it. 

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Anonymous B on Apr 03, 2024

Firstly, although this sort of mini-case or brain teaser may still happen with smaller strategy consulting firms, it is extremely unusual mario games and will never happen with any larger strategy consulting firm due to their inherent limitations in terms of the breadth and depth of the skills that can be tested. Not only that, I agree with you, and I think I would have done the same thing by looking at the value chain and counting the quantity of water needed to make each "product" along the way.


Paul gave the best answer


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PL-level BCG experience (6 years)|Interviewer at BCG| 6/6 personal + 95%+ candidates offer success rate
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