MBB Interview on Zoom&Video Call for Quantitative Questions

MBB quantitative zoom
Neue Antwort am 14. Dez. 2020
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fragte am 11. Dez. 2020
Preparing for Bain interview

Hi All,

I am wondering how efficient solving quantitative such as calculations from big tables during online interview. I am preparing for MBB and I have practiced with many from this platform. If there are two exhibits to show it get really complicated from my experience during online interview. Any ideas for quantitative sections how it is conducted or expected?

Kind Regards

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antwortete am 11. Dez. 2020
McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School


For math you should:

  1. Present the interviewer your approach (formula, calculation steps, equation, etc)
  2. Check with him whether the approach is correct
  3. Start calculations
  4. Come back to the interviewer with some midpoint numbers to keep him engaged and to make sure you are on the right track. Also, it makes sense to check what is his tolerance for rounding the numbers
  5. Present the final answer

Basically, you need to develop 3 calculation skills:

1) Learn how to multiply double-digit numbers (https://www.youtube.com/watch?v=6ndkkPZYJHo).

2) Learn how to work with zeros. Best way - always use 10^power instead of zeros


300x9000 = 3*10ˆ2 x 9*10ˆ3=3x9*10ˆ(2+3)=27*10ˆ5

Handwritten it looks not that complicated. If you get used to writing all the numbers that way, you will never loose zeros and all multiplications/divisions will be replaced with + or -.

3) Learn the division table up to 1/11 (i.e. 5/6 = 83.3%). It will help you calculate any percentage problems. For example, if your market is $620M and your revenues are $51M you can use 5/6 as a proxy to calculate the market share

Here is a set of formulas you should know:

  • Interest rates calculations
  • Compound margin
  • NPV using the Rule of 72, Perpetuity
  • CAGR using the Rule of 72
  • Currencies exchange calculations
  • Speed, time, distance calculations
  • Equations, systems of equations
  • Ratio & Proportions
  • Little's Law
  • Solving the problems by calculating the area of the triangle
  • Profit / breakeven formula
  • Correlations, outliers (being able to spot on the graphs, tables)

For an exhibit (table / graph) You can use the following approach:

  1. Take a minute to look at the graph
  2. Read the graph title
  3. Look at the graph type and define the type (pie chart, line chart, etc)
  4. Look at the legend (ask for clarifying questions if necessary)
  5. Identify whats going on on the graph. Look for: Trends, % structures,
  6. Look for unusual things - correlations, outliers,
  7. Make 3-4 conclusions from the graph. Think of potential hypothesis on what could be the root cause / what are the consequences
  8. Prioritize the most important for your current analysis and move forward with the case

Sources to learn from (prioritized):

  1. Study "Say it with Charts" book by Barbara Minto
  2. Learn basic statistics (Any GMAT or MBA prep guides)
  3. Check all available MBB presentations and publications. Practice to derive conclusions and check yourself with the actual ones from the article / presentation
  4. GMAT IR part (Official guide and Manhattan prep)
  5. "Consulting Bible" and "Vault guide for consulting" - check the chapters on cases with graphs in these books

Good luck!

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Content Creator
antwortete am 11. Dez. 2020
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

Hi Gurkan,

The question here is really how to do you structure your math! There is no difference between the online and the in-person experience here.


First: Use tables for multi-dimensional data


If the interviewer gives you linear data, you can simply jot it down on the LHS. However, if they say, for example "We have 4 main costs", you better be setting up a table ASAP! Those 4 costs will be your rows, and any additional information given will be in each respective column.

Not only will this help you write down all of the information quickly AND keep track of it, but it will help you figure out where to go next!

By the way, the same applies for exhibits. Write down the key information back onto your sheet!


Organize all of your notes in a casing template

1) A seperate sheet for each "portion" of the case...with clear locations + methods for title/subject, notes, calculations, takeaways, etc.

2) Figuring out a location for everything and where each information type should go

3) Seperate sheet for math calculations


Third: Learn to quickly take notes down


1) Decide physical vs virtual - are you a faster typer or writer?

2) If virtual, pick the best tool - try outlook draft emails (so you can store/organize with your email), try notepad, try a tablet so you can write on it, etc....find the one that works for you

3) Only write down what is important - you should know this! You don't need to capture everything. Just like in a case, figuring out what information is not needed is just as valuable as figuring out what information is needed.

4) And then, what you do write down, write it in shorthand!

I.e. If I say "Your client is Bills Bottles. They earn $800M in profits each year by manufacturing bottles to soda companies in the US and Europe. Over the past two years they've seen profits falling and have brought you in to investigate"

You should write:

  • Bills Bottles
  • Manufacture
  • Client = soda comp
  • 800M P
  • P [down arrow] 2 yrs
  • US + Europe
  • Obj: Fix P
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Content Creator
antwortete am 11. Dez. 2020
#1 Coach for Sessions (4.000+) | 1.500+ 5-Star Reviews | Proven Success (➡ InterviewOffers.com) | Ex BCG | 10Y+ Coaching

Hi Gurkan,

There are no differences with the face-to-face interview in the general approach on how to deal with math. However, the interviewer cannot see your notes, so you have to be very clear in your communication.

In terms of how to approach math in the case, this is what I would recommend:

  1. Repeat the question – sometimes candidates do mistakes answering the wrong question
  2. Ask for time and present how you would like to proceed from a theoretical point of view. If you find challenging to do this with graphs, it may be you should approach graph analysis differently. I listed below the steps I would recommend for it. If you find challenging to read the data since they are in screensharing, just mention to the interviewer you need more time/have to go back to one of the graphs as you could not read all the data shown
  3. Perform the math and present the interim steps to keep the interviewer aligned – don’t just say the final number
  4. Continue with the computations until you find the final answer
  5. Propose next steps on the basis of the results you found

In terms of general math tips and avoiding mistakes, I would recommend the following:

  1. Use correctly 10^ powers in your math computation. For example 3.2B/723M can be transformed in 3200*10^6/732*10^6, which makes it easier to deal with math
  2. Ask if it is fine to approximate. When you have to deal with math in market sizing - and sometimes even in business cases - you are allowed to approximate math to simplify the computation. In the previous example you could transform the computation in 320*10^7/70*10^7
  3. Keep good notes. One of the reasons people do mistakes with big numbers is that they don't keep their notes in order and forget/misreport numbers
  4. Divide complex math in logical steps. This is something you can use for big numbers after the application of the 10^ power mentioned above. For example: (96*39)*10^6 à 96*40 - 96*1 = 100*40 - 4*40 - 96*1 = 4000 – 160 – 100 + 4 = 3744*10^6
  5. Use shortcuts for fractions. You can learn by heart fractions and thus speed up/simplify the computation - the most useful to know are 1/6, 1/7, 1/8, 1/9.

I would also recommend to practice math under pressure - not just math. Many candidates are totally fine doing 67% of 67 in normal conditions, but freeze if you ask this suddenly in a case interview.

In order to do so, try always to use a timer with a strict time constraint when you practice math – this will create pressure and help to replicate the actual conditions of the interview.

In terms of how to deal with graphs I would recommend the following:

1. Read the graph

  • Ask for 30 seconds to understand the graph
  • Summarize what the graph is about. Read in particular the graph title (often forgotten), the axes and the legend

2. Analyze the graph and find the main insights

  • Repeat the question you have to answer. Many people don’t spend time to clarify the question; consequently, they answer the wrong question. Don’t be one of them and be sure to restate what is the main insight you have to derive
  • Provide an analysis related to the question. Analyze how the graph can help to answer the question you just repeated and provide an answer. Here is where you may have to use the math approach listed above

3. Propose the next steps

  • State your hypothesis or suggestion or what to do next. As a last step, a great candidate will present what should be done next to help further the client
  • Ask a question related to what you need to move forward. This will show you are a proactive candidate

Hope this helps,


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Gurkan am 11. Dez. 2020

Thanks a lot!!

Content Creator
antwortete am 11. Dez. 2020
Accenture, Deloitte | Precision Case Prep | Experienced Interviewer & Career Coach | 15 years professional experience

Hi Gurkan,

Agree with Henning that this should NOT be complicated over Zoom. Ask the interviewer to slow down or show you the data again if its not easy for you. From what am hearing over past 3 months, interviewers have been mindful about this. One tip from me will be to have white A4 papers and black pens handy. Write clearly and dont be afraid to show your workings over video or just provide commentary.

When it comes to quant keep it simple, think as follows:

  1. % changes
  2. Averages
  3. Trends- upward, downward, staying same
  4. Correlation between data (positive, negative, neutral)
  5. Rounding (but align with interviewer before you do this)\

Have a look at this thread too: https://www.preplounge.com/en/consulting-forum/virtual-interviews-8321

All the best!

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Content Creator
antwortete am 11. Dez. 2020
Ex-Mckinsey|Certified Career Coach |Placed 500+ candidates at MBB & other consultancies

Hi there!

First of all, good luck with your Interview!
Don`t worry. It will not be so difficult. You can always ask the interviewer to slow down, repeat the information, go back to the previous slide. Don`t forget to prepare a pen and a notebook for small notes.

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antwortete am 11. Dez. 2020
Bain | passed >15 MBB interviews as a candidate

It's actually not that difficult. If it's not too many numbers, just note down the numbers from one exhibit and do the calculation while looking at the others. Totally OK to ask the interviewer to show one specific slide.

And I doubt that any interviewer will go through a case on zoom that requires matching numbers from two large data tables on two separate slides. If that would be the case, expect them to have figured this out after 10 months of zoom interviews and adjust the case if necesary.

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Content Creator
antwortete am 14. Dez. 2020
McKinsey | NASA | top 10 FT MBA professor for consulting interviews | 6+ years of coaching


In interviews the aspect which causes more errors is pressure: start to solve calculations with strict time constraint. For longer formulas always share the calculation structure with the interviewer before starting to write down the numbers: this helps to take time, to reduce the pressure, and gives you the opportunity to receive a first feedback from the interviewer avoiding wrong calculations.

I recommend practicing with:
- Preplounge math tool: https://www.preplounge.com/en/mental-math.php
- Youtube channels with math tricks:


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Content Creator
antwortete am 14. Dez. 2020
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut


Indeed the quant part is the nightmare for many many candidates. However, it should not be harder on Zoom than in person, and you can always regulate the speed

I would strongly recomment you practice it with the Integrated Reasoning part of the GMAT exam.

There are free exams in the internet that you can use for practice (the one of LBS MBA page, Verits prep, as well as some free trials for courses such as the one of The Economist (https://gmat.economist.com/)

Furthermore, you can leverage the MBB tests (https://www.myconsultingoffer.org/case-study-interview-prep/bcg-online/, https://www.psychometricinstitute.co.uk/Free-Aptitude-Tests.asp, and many others)

Hope it helps!



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McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School
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