how to improve at math structuring?

Math problem
New answer on Oct 08, 2022
6 Answers
Anonymous A asked on Oct 05, 2022

- I do well in qualitative structuring (in the beginning) 

- I am good in mental math 

Taken two and two together, however, I am not good at solving the quant sections during the case. 

Typically I lack the structure to put up the calculation nice and presentable and in the middle often start to get scatter brained and not good to follow before I eventually arrive at the right solution.

Overview of answers

  • Upvotes
  • Date ascending
  • Date descending
Best answer
Content Creator
replied on Oct 05, 2022
MBB | 100% personal interview success rate (8/8) and 95% candidate success rate | Personalized interview prep

Hi there,

How to structure math in a case

  1. Have a seperate "math" scrap sheet of paper
  2. Grab a new sheet of paper every time you're entering a new phase of the case...number and title it
  3. Use tables to organize numbers
  4. Write out the equation before doing the math
  5. Never forget to write down units
  6. Circle key numbers AND write down the "so what"

How to practice math

Most casebooks have a section on math...but I wouldn't rely on this for your prep.

  1. 100% Recommend Rocket Blocks
  2. Online "Drills": (Sites like JetPunk and Preplounge)
  3. In addition to that, you can ask other PrepLoungers to case you on math-heavy cases. You can also search for those case types here and work through them yourself.

Some key math formulas/concepts:

  • Breakeven
  • NPV (with + without growth, perpituity + 1-2 years from now)
  • % Change
  • ROI
  • Margin
  • Markup
  • Inventory turnover


Some great answers from a variety of angles have already been asked. Check these out!

Mental Math

Conceptual/Contextual Math

Was this answer helpful?
replied on Oct 07, 2022
McKinsey San Francisco | Harvard graduate | 5+ years of coaching| Free 15 min intro call | Personalized approach


Sounds like you've been able to pinpoint exactly what it is you struggle with, which is a great start! I would do some focused practice on the quantitative portions of the case (i.e., for some targeted practice, find a case, listen to/read the prompt - or however much info you need to solve the quant part, and then just solve the quant part, don't worry about the rest). 

  • Start by taking the time to understand what you are being asked to solve. Do you understand what calculations you will need to do?
  • Once you have figured out how to approach the calculations, think about how you can set it up cleanly on a page, and talk the interviewer through what you are going to do. For instance, you might want to draw a table, or just set up some sums or multiplications.
  • Once you've sorted through your approach in your head and got the method down on paper, proceed by solving through your set-up.

I don't think there's one single way to approach the quant part, as long as you are clear and methodical in your process, so go with what feels most intuitive for you. I would recommend starting to build up this muscle by practicing taking your time with it first, and then speeding up as you get more comfortable. If you are comfortable with the mental math already, it should just take some targeted practice to help you improve. 

Was this answer helpful?
replied on Oct 05, 2022
Bain | EY-Parthenon | Roland Berger | FIT | Market Sizing | Former Head Recruiter

You have to practice the right way. Meaning that you always have to come up with a formula before doing any calculation:

  • First solve in abstract creating a formula or equation
  • Only then proceed to any calculation

This is the process. Now you have to practice a lot. There are no turnarounds to this.

Was this answer helpful?
replied on Oct 05, 2022
Incoming BCG Principal | Former Bain, AlixPartner, and Private Equity | INSEAD MBA | GMAT 780

To properly answer your query I should see you in action.
However, starting from what you mentioned, I suggest that you should:

  • Identify 3 exercises
  • Solve them very slowly trying to be as clear in your thinking as possible
  • Review them in “interviewer mode"

If you want, feel free to schedule a coaching call with me, I can give you a discount in case.

Was this answer helpful?
Content Creator
replied on Oct 08, 2022
Ex McKinsey EM & interviewer (5 yrs) USA & UK| Coached / interviewed 200 +|Free 15 min intro| Stanford MBA|Non-trad

So first off I highly recommend writing the methodology that you're going to follow on your paper and then walking the interviewer through this before starting. That way they can course correct you if it looks like. you might be heading off in the wrong direction. Write it down one side of your paper (probably the left). 

Then go through it very methodically, keeping calculations to the right of the paper and underlining / circling the answers to each part of the methodology as you go through so that you can come back to the right number in the next step. Talk the interviewer through what you're doing so that they can keep up with your thought process and, again, course correct if need be. 

Hope that helps - I'm happy to talk through if it'd be helpful! 

Was this answer helpful?
replied on Oct 06, 2022
Ex-Mckinsey (analyst->associate->manager) and now in tech (Bytedance) + Part time interview coach and mentor

Hey there,


Here are a few tips for you:

1- You shouldn't go into calculations before putting in place your structure. 

For example, if you're about to calculate the profits, split it into revenues and costs. Understand where the revenue is coming from (e.g., number of rides and price per ride) and what the costs are (e.g., fuel, tolls, registration etc.,) before going into the math. 

- Always use visuals for your structure (e.g., in the example above, you can use a tree breaking down the “P" into “R” - “C” and the R/C into the various components.

2- Once you have the structure in place, source the datapoints/inputs (ask questions to ensure you get all the inputs you need before running the math

3- When you get to the actual math, check with the interviewer if he/she requires exact figures or not, then take some time to run the numbers (30sec to 1min).

- Any detailed calculation should be done separately (not on the main structure) with the structure kept only for final clean figures. 

- Do not use figures with more than ~4 digits (use K, M and B) to keep your numbers short and clean (e.g., 5,000,000 x 7,000 = 5Mx7K=35B

4- Present your findings top-down, starting with the answer (the profits are equal to x) and then summarizing your approach/inputs.


Best of luck,



Was this answer helpful?
Ian gave the best answer


Content Creator
MBB | 100% personal interview success rate (8/8) and 95% candidate success rate | Personalized interview prep
Q&A Upvotes
95 Reviews