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Can You Crack the Hardest Case Interview Questions?

hardest case interview questions

Submitted by global_admin on Tue, 04/30/2019 - 10:27
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Ah, the case interview. It’s what separates the wheat from the chaff, the men from the boys, the future CEOs from those destined to forever toil as analysts. But case studies and case studies interview questions are like vegemite - while some simply can’t get enough, others are left with a bad taste in the mouth.

Whichever side of the equation you fall on, case interview questions are an integral part of the strategy interview process - and therefore unavoidable if you are looking to climb the corporate ladder (or even just reach the first rung!) In fact, thanks in part to the curly cases included, McKinsey has been rated by Glassdoor as the toughest business on earth when it comes to job interviews - for the second year running!

And it’s not just strategy consulting firms who incorporate a case - most of our industry clients will also throw one of these questions into the process to assess potential applicants. So it’s worth brushing up on those case interview questions! And what better way to do so than tackle this, the most difficult case study ever advanced (according to a couple of very smart cookies):

Can any two dogs in the world have the same number of hairs?

adorable animal breed


The answer is actually a relatively simple mathematical theory, the Pigeonhole Principle (expanded here for any true maths nerds among us!) 

Some other top contenders for “most difficult” award:

  • How much would you pay for a London - NYC trip which takes 10 minutes?

  • Should the University of Chicago launch online courses?

  • Should China Southern Airlines introduce a direct Perth - Guangzhou flight?

  • A small Internet Cafe in Ghana’s capital Accra is experiencing a decline in profits - what do you do?

So, how did you fare? If you struggled with the “hardest” question (or any of the others), here are four ways to improve your case interview skills, straight from the horse’s mouth! (The “horse” here obviously denoting successful and experienced strategy professionals):

1. Case Interview Questions: Practice, practice, practice

We can’t emphasise this strongly enough. No matter what stage of your strategy career you are at, the case interview question requires a set of skills not utilised in the day to day. There are a wealth of resources out there to help you prepare - sample cases, suggested approaches, interviews with successful candidates, even regularly updated detail around which consulting firm asks what! ConsultingCase101 has is all, as does Victor Cheng’s

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With such a goldmine of information literally clicks away, you would be silly not to thoroughly prepare. Rope a friend or family member into playing the part of interviewer, or practice speaking into the mirror - either way, taking the time to do a “dry run” of a few cases will make a world of difference on D-Day.


take your time at beginning


2. Take your time at the beginning

Case interviewers will regularly be given a sheet of information which they are to share with candidates - if  the candidate asks for it.

If you are receiving a verbal question, feel free to pause after the initial question and repeat it back, to clarify you have understood. That could go something like this:

Interviewer: “Please calculate the total size in dollars of the wedding dress market in Australia for one year”

Interviewee: “Just to clarify, you want me to tell you the size, in Australian dollars, of the wedding dress market for one year in Sydney?”

Seems repetitive, I know, but it a) confirms you understand the question and b) buys you an extra 30 seconds thinking time. This is also an opportune time for you to test assumptions and ask for further clarification - in the above example,  this could be questions along the lines of:

“I’m assuming we are talking about any garment worn by a female on her wedding day, not just traditional ‘white’ wedding dress, would that be correct”?

Most interviewers will give you 5-10 minutes after question has been asked for you to confirm, clarify and question. So use it! Finally, if there is any ambiguity in the question, address it now. For example:

How much would you pay for a London - NYC trip which takes 10 minutes?

Does this mean, how much would you PERSONALLY pay? Or how much an airline should charge for this? Make sure you appreciate what exactly is being asked, so you aren’t sent on a 50 minute wild goose chase!

3.Don’t over complicate the numbers

don't over complicate the numbers

Many consultants make the mistake of trying to be overly specific or accurate. Don’t choose a ridiculous number as your proxy (for instance, you’re wise to learn the population of the city in which you are interviewing for the purposes of market sizing - don’t claim Sydney as population of 1 or 100 million), but similarly don’t sweat it if you don’t have an exact approximation.

The way to legitimise an otherwise inexact estimate is outlined below - essentially, state the number you are using, why you have chosen it, and clarify where you would get the actual figure from if you had access to further data. And if you are choosing an arbitrary number, you may as well make it an easy one! So if 1000 and 1500 are both legitimate choices, stick with 1000.

It’s important to emphasise here - it’s the structure, the story, and the process that matters, not the end number. You can get the answer absolutely spot on in terms of number, but if you haven’t taken your interviewer on a journey and demonstrated how you are actually approaching the problem, you haven’t succeeded. You are a human, not a calculator - capitalise on this!

4. Make it personal and creative

Finally, case studies are a test of your logic, the structure of your thinking, your mathematical ability - and your creativity. May seem counter-intuitive, but trust me - this is what sets you apart!

It’s likely that everyone undertaking the case interview has an undergraduate degree with impeccable academics, an MBA from a prestigious business school, and probably a few years’ industry experience from a well regarded international brand. So what will make you stand out from the other over achievers? Your ability to weave a narrative.

Grounding your figures in personal experience also helps cover your back, in case your numbers aren’t quite spot on. An example of this (in analysing a case about the size of the wedding dress market in Australia):

“I am fixing the price of the average wedding dress at $2500. I choose this figure because I have two close friends who have recently married; one whose dress cost $2000 and one whose dress cost $3000”.  

Finally, think outside the box. In our above wedding dress example - what about non-christian religions who dress in other forms of clothing on a wedding day? What about same sex weddings in which both/neither participant wears a dress? Take 5 minutes to brainstorm “spanners in the works” - and even if you don’t have time to dissect them completely, at least flag that you have considered these possibilities.

So, there they are. The most difficult case interview questions I have encountered, and how to tackle them. I’ll leave you with a final question, for you to have a go (and send me your answer, if you dare!):

The American NBA is considering expanding into China.. Should it?

For a confidential discussion about your next perfect strategy role, or for more insight and advice about preparing for your next case interview, reach out to me or another member of the Morgan McKinley strategy team.


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