Struggling with Mental Math - Should I Give Up on Consulting?

Hi there,

First of all, I am sorry to hear about your struggle with math!

I would be happy to share my thoughts on your situation:

• First of all, I would advise you to keep practicing and not giving up. You've already made progress and math is pure craftsmanship that can be perfected quickly and easily.
• Moreover, consider using structured practice tools. There are several apps and websites like PrepLounge’s Mental Math Practice designed specifically for improving mental math skills, which can provide you with a focused way to hone this skill.

You can find more on this topic here: Speed reading techniques.

If you would like a more detailed discussion on how to best prepare for your upcoming interviews, please don't hesitate to contact me directly.

Best,

Hagen

Publishing this anonymously because I'm basically in the same position. I'd love to work in management / strategy consulting but my mental math isn't that great.

I'll say the one thing that has helped me was caseinterviewmath.com - yes, it can be stressful, but I try do 30 minutes a day so I get comfortable with the uncomfortable. 

I recommend this mental math cards app. It's available on iOS and I try practice 3-5 times a day with mixed operations. It's very practical and you can keep track of speed and accuracy.

My advice is not to give up. Keep going because you can always improve skills like mental maths. I hope other people add their own replies too to help you out :) Best of luck!

Hi there,

Don't worry. 

Most case candidates don't do well in mental math when they start out. It's a skill that rests unused since early school days.

The good news is that it's easy to wake up again and practice.

You mentioned that you have worked through 7 practice cases, I assume including all the other elements besides math. If I understood this correctly, this is the least effective way to practice mental math.

If you want to practice an individual skill, there is no need to practice 95% of unrelated elements every time you want to calculate something.

What you need is

• a strong theory foundation on how to approach case math and calculate quickly and accurately
• Ample practice opportunities in the form of targeted drills where you go through many multiplications, divisions, additions, subtractions, averages, in bulk under timed conditions

If you isolate the important exercises and then work through many similar math problems back-to-back, that's when you train the right skill in the most efficient and effective manner, same as when you isolate muscles in the gym.

As for the mindset, consider working with a coach, the timer on your phone or in peer case sessions ask your partner to only give you math problems to work on, not full cases.

Please reach out for some more targeted advice or a free math drill generator that does the "finding good practice materials work" for you.

All the best,

Florian

Hi there!

I feel your concerns and struggles. But there are two good things you should keep in mind: (1) As you said yourself, you can handle math — you've proven that you can, and (2) mental math is one of those things that definitely gets better with practice. So, overall, I would say don't give up — definitely not because of mental math! You can fix this with rigorous, dedicated practice.

From your question, it seems to me that you have a bit of a confidence problem with math, which is why you get stressed with it in an interview setting. But this is very fixable. You need to get a point where the mental math becomes second-nature to you, so that you wouldn't need to consciously "think" about how to solve a problem when you first look at it. That'll take the pressure off of you during interviews too.

To get there, try to first focus on accuracy and then on speed. Try to get everything right — consistently and all the time — before you start applying time pressure on yourself. See what sort of questions are tripping you up most frequently, identify those weak areas, and practice them tirelessly. That'll help you intuitively develop a process for how to approach different types of math problems. Eventually, the mental math process will become second-nature to you, and that's when the speed improves. The less you need to "think", the faster you get — it's like muscle memory! 

Please feel free to reach out if you need help in identifying your problem areas and how to fix them. I've had a lot of experience with the GRE too, so I understand this world quite well.

Good luck!

It's like training for a 10K. When you start you might not be able to run more than 10 minutes, but through repeated exposure you will expand your capabilities.

Mental math for consulting is not that demanding, or in other words, the concepts that you need to grasp are usually learnt in the first 6 years of schooling, meaning that a 11 year old student knows the concepts required to execute all of the required calculations for a case interview.

The "difficulty" is that you need to become proficient at that skill. And for you, since it's a "muscle" that you haven't trained much, that means daily practice (15-30 mins /day EVERYDAY) for a few weeks. 

Please notice that in your case, you probably not only need to train arithmetic (i.e. calculations) but also solving a lot of equations (those type of break-even analysis, payback time, etc.) - but you have to start with arithmetic.

It may feel hard at this point, but the truth is that of all the skills one needs to have to successfully pass a case interview, this is one of those that you can acquire "easily" through daily consistent practice in a straightforward way.

Hi there,

Your frustration is understandable but you definitely should not give up based on the context you provided.

Firstly, case mental math is not something that comes naturally to a lot of candidates at the beginning of preparations. Secondly, it appears you have not yet spent enough time doing targeted practice. Thirdly, you have ample time to improve your mental math abilities drastically.

My suggestion on how to approach this situation involves the following:

1. Seek and identify resources for targeted mental math prep (e.g. apps with tips on swift multiplication, handling percentages, etc.)
2. Find a coach or experienced case preparation partners that can provide quant-heavy cases with specific targeted feedback for improvement
3. Iteratively run sessions with a mix between isolated drills with the earlier identified resources and full cases with heavy calculations so you can simulate the pressures of an interview

In my experience with candidates, the only way to improve and reduce the pressure in an interview is via quality repeated exposure so you have to work through sucking at first to get better.

Feel free to let me know if you need help identifying specific resources or coaching support.

All the Best

Fathu 

Hi there,

this is really the one discipline that you can tremendously improve by repetition. It's quite normal to be rusty in the beginning. But if you make a concerted effort every day in your case, to practice mental math, you'll be in good shape for the case interviews.

I'd be much more concerned about your self-doubts so early in the process. You say that "consulting is your biggest dream" and yet you are already floating the possibility of giving up on that dream because you cannot (presently) juggle around some numbers in your head quickly enough. This is definitely not a consulting mindset! 

In an actual consulting job, you will be confronted with challenges on a daily basis and you have to figure out ways to deal with them. If this makes you uncomfortable, then consulting might not be the right track for you. Otherwise, you can view your mental math struggle as an exemplary challenge and already get some practice in problem solving for the actual consulting job that you are pursuing.

Best of luck

Hi there,

Q: Should I give up because I’m struggling with mental math?

One note before answering your question: you can always write down the math unless the interviewer explicitly asks you to do the math in your head, which is quite rare. For this reason, I would recommend prioritizing how to approach math and avoid mistakes rather than mental math.

Now, answering your question: no need to give up just because you are struggling with math. Performing math under pressure is a skill that you can develop. If you have done drills and see some improvements, you might just need to do more of them.

As next steps, if this is your main area of weakness and the rest is fine, I would prioritize math drills over full cases, until you have fixed the main issue there. The reason is that while you might cover one or two math questions in one hour if you do full cases, you might cover far more by doing drills. If you continue to practice in that particular area, eventually you will see improvements.

I reported below some extra tips for math in case interviews, in case they might help.

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1) How to approach the math in a case

As a general approach to answering a math question, I would recommend the following:

1. Repeat the question – sometimes candidates do mistakes answering the wrong question
2. Ask for time and explain how you would like to proceed, presenting the formula you want to follow
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 calculations until you find the final answer
5. Propose next steps based on the results you found

2) Avoiding mistakes

Below you can find some tips to avoid mistakes:

1. Use 10^ to account for zeros. For example, 3.2B/723M is equivalent to 3200*10^6/732*10^6, which helps to do the math correctly
2. Ask if it is fine to approximate. The interviewer may allow to approximate the numbers to simplify the math. In the previous example, you could approximate as 320*10^7/73*10^7 and simplify the computation
3. Keep good notes. One reason why candidates make math mistakes is that they don't keep their notes in order, thus forget/misreport numbers
4. Divide complex math into simpler steps. If you have to calculate (96*39)*10^6, you can change the math as 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 speed up/simplify the computation - the most useful are 1/6, 1/7, 1/8, 1/9

3) Formulas useful to know

I reported below some of the most common formulas that appear in case interviews, in case you want to review them:

• Breakeven
• NPV/Perpetuity formula
• ROI
• Rule of 72
• Simple and compound growth rate

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Good luck!

Francesco