Bombed two cases (case math), any tips on how to improve?

case math First Round Math problem second round
New answer on Feb 28, 2023
8 Answers
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Anonymous A asked on Feb 21, 2023

Hi everyone, 

I recently got rejected at two MBB interviews. One time in a first round interview and the other in a second round. I am still motivated to continue, and have a couple of first round interviews scheduled in the near future. 

I have practiced about +- 35 live cases to date.

The feedback I got was mainly related to the mathematical part of the case; I underperform when I get a conceptual math problem. I seem to lock up and cannot get to formulating a proper approach to solve a relatively easy problem. The arithmetic part itself is not an issue, it is mainly coming up with a specific formula or approach to solve conceptual problems. 

With the more common business cases such as market entry, revenue/profitability etc. I feel like I am at a high level. The structuring and brainstorming elements of cases are also going pretty well. 

The main questions I struggle with all have the same structure: With not so many context, I get a lot of data (or have to ask for it), and I get a pretty basic questions about the data, after which I have to structure and come up with an approach to the question. 

For instance in the second round interview I got a question similar like this;  A lion lives on an island and only eats cows: how many cows must there be on the island for the lion not to die of hunger?

I knew that I had to ask for the following elements: 

  1. how many cows does a lion need to eat each year
  2. how long does a cow live
  3. how many calves does a cow pair get every year. And at what age can they produce calves.
     

It is the next step, where I have to lay-out a formula or structure where I just lock/choke and have no clue how to continue. 

Does anyone have any tips on how I can practice this crucial element? 

Thanks in advance. 

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Hagen
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Content Creator
replied on Feb 22, 2023
Ex-Bain and interviewer for 7+ years | >95% success rate | mentor and coach for 6+ years

Hi there,

First of all, it’s great to see your level of motivation despite the two rejections!

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

  • I would highly advise you to reach out to a coach about your issues, especially when it comes to more conceptual skills where you lag behind. With 35+ live cases, I would not have expected you to still struggle with such a variety of aspects, whether big or small. As such, I am not sure whether continuing to prepare the same way you have done it thus far (alone) will help you solve your issues.
  • Moreover, I would highly advise you to work on your weak spots separately and also prompt the peers you practice with about them. This way, you will not feel too much pressure on the aspects you want to improve further, and your peers will know what to watch out for in particular.

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

Best,

Hagen

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Rushabh
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replied on Feb 22, 2023
Limited Availability | BCG Expert | Middle East Expert | 100+ Mocks Delivered | IESE & NYU MBA | Ex-KPMG Dxb Consultant

Hello,

It seems like you've reached a plateau in your preparation. This is fairly common because there is a limitation to the kind of cases your peers can give you and the depth of feedback you receive.

If I was in your position, I would take a few sessions with a coach to practice some difficult cases with, get an action plan on how to tackle these weaknesses and get extensive feedback as your improve.

Hope this helps and happy to help if you wish to work together!

Best,

Rushabh

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Francesco
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replied on Feb 22, 2023
#1 Coach for Sessions (4.000+) | 1.500+ 5-Star Reviews | Proven Success (➡ InterviewOffers.com) | Ex BCG | 10Y+ Coaching

Hi there,

Q: It is the next step, where I have to lay-out a formula or structure where I just lock/choke and have no clue how to continue. Does anyone have any tips on how I can practice this crucial element? 

First of all, well done on identifying the issue – that’s key to improve.

Given what you shared I believe you can do two main things if you want to self-study:

  • Before the interview. Do drills on math questions similar to those you find challenging. You can take a few good casebooks and just review the math part of the cases, ignoring the rest. After a certain number of drills you should be able to structure more easily. If you just do the math and skip the rest, you should be able to do several drills in a short amount of time and improve faster.
  • During the interview. Even if you do drills, you might still get stuck. If that happens, you need to explain clearly to the interviewer the goal and input you want to use, and clarify what you don’t understand in terms of getting the result. If you frame this correctly (how you communicate it is key), the interviewer will help to unlock the part you find missing and solve it faster. 

Hope this helps,

Francesco

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Ian
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Content Creator
replied on Feb 22, 2023
MBB | 100% personal interview success rate (8/8) and 95% candidate success rate | Personalized interview prep

Hi there,

First of all, if you really care that much about this job, hire a coach! Compare the investment to the salary and signing bonus in just the first year, let alone the impact on all your future earnings and career potential.

Here are some of my major takeaways:

  1. You seem to struggle with market sizing. Make sure you pratice this. Here's some practice
  2. With math, I highly recommend rocketblocks (but please don't use them for frameworking!)
  3. It sounds like you're case prepping wrong. Read this to adjust
  4. Here's some case reading too in case you're not approaching cases right
  5. Get a coach! They'll make the difference here…how can an individual ever self assess? We don't know what we don't know!
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Victoria Christine
Expert
replied on Feb 23, 2023
1st&2nd Session 50% off|BCG Consultant ME|President of the Consulting Club|Esade MBA |Offers from McKinsey & BCG

Hello A,

  1. One approach could be to do more practice cases that specifically focus on quantitative or mathematical problems. You could also try to break down the problem into smaller parts and identify any relevant formulas or concepts that may apply. 
  2. Another tip could be to work on your mental math skills, which may help you approach the math problems more efficiently. You can practice mental math exercises online or using apps, and try to incorporate mental math into your daily routine. 
  3. Finally, you could consider seeking feedback from a case interview coach or mentor who can provide more targeted guidance on how to improve your mathematical problem-solving skills.

Best of luck!

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Pedro
Expert
replied on Feb 27, 2023
Bain | EY-Parthenon | Roland Berger |Former Head Recruiter | Market Sizing

You need to train issue trees. A lot. And there's only one way to do this. It's not about about finding a great tip that will sort this out for you.. It's about putting the effort and practice the kind of problems you struggle with. You basically need to develop your brain into being able to solve any type of problem like this.

So you first take the time to find the solution. I am sure you'll find a way to get there. Might not be the fastest route, but one that gets you there. 

Then you go back to the start and take all the pieces and calculations you did and think about how you would structure this in the most efficient way, in an issue tree sort of manner. Then you do this for a ton of problems until you start getting this immediately.

 

Solution to the problem:

Number of cows the lion eats during his lifetime is:

Number of years the lion lives * Number of cows he eats per year.

 

You took a somewhat different route (which seems to assume a lion lives forever, so there needs to be a constant number of cows in the island), so I'll solve using that process as well:

Cows lion eats per year = number of cows * average number of calves a cow has per year 

Average number of calves a cow has per year = number of calves a cow has during its life / number of years a cow lives.

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Cristian
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replied on Feb 22, 2023
#1 McKinsey Coach by rating & recommendation rate

Hi there, 

Sorry to hear that the interviews didn't work out but congrats on figuring out what the core problem is. Often times that means  it's half solved. 

Based on your description it rather sounds like you don't have a clear technique of approaching calculation questions (which is normal - most candidates don't). 

At this point, it might be a great ROI for you to get some coaching support to change your approach to calculations. If this is not within your budget, happy to share with you (for free) a guide I wrote on how to approach calculation questions in stages (thus lowering the potential of making mistakes and improving the communication with the interviewer). 

Best,

Cristian

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Benjamin
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Content Creator
replied on Feb 28, 2023
Ex-BCG Principal | 8+ years consulting experience in SEA | BCG top interviewer with ~5 years of interviewing experience

Hi there,

Sorry to hear about your rejections but glad you are still pressing on. Solving quantitative thinking or conceptual quant is definitely not an easy task. 

Like many other coaches have mentioned, I don't think you will get the answer to your problem here through responses, as part of solving the problem involves understanding the challenges → understanding the right approach → practicing → getting good feedback.

This is one of the areas I had also to struggle with and overcome, both while applying and on the job. Having failed math in pre-university and studied a liberal arts subject in university, quant was not one of my strong points. But definitely possible through practice and right guidance. Don't give up!

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Hagen gave the best answer

Hagen

Content Creator
Ex-Bain and interviewer for 7+ years | >95% success rate | mentor and coach for 6+ years
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