Cookie and Privacy Settings

This website uses cookies to enable essential functions like the user login and sessions. We also use cookies and third-party tools to improve your surfing experience on preplounge.com. You can choose to activate only essential cookies or all cookies. You can always change your preference in the cookie and privacy settings. This link can also be found in the footer of the site. If you need more information, please visit our privacy policy.

Data processing in the USA: By clicking on "I accept", you also consent, in accordance with article 49 paragraph 1 sentence 1 lit. GDPR, to your data being processed in the USA (by Google LLC, Facebook Inc., LinkedIn Inc., Stripe, Paypal).

Manage settings individually I accept
expert
Expert with best answer

Clara

100% Recommendation Rate

59 Meetings

16,389 Q&A Upvotes

USD 229 / Coaching

4

Hi coaches, could you plz provide some advise for improving mental calculations?

4 answers

  • Upvotes
  • Date ascending
  • Date descending
Best Answer
Book a coaching with Clara

100% Recommendation Rate

59 Meetings

16,389 Q&A Upvotes

USD 229 / Coaching

Hello!

The best is to practice, practice, practice! I could recommend you to start with:

1. GMAT exams: that can be found for free in the internet (GMAT prep with The Economist, London Business School free trial, etc.)

2. Math tools: such as Mimir math for iOS or Math tool on Viktor Cheng´s website)

3. Multiplying any two 2 digit number in 3 seconds: check this great video > https://www.youtube.com/watch?v=6ndkkPZYJHo

Best,

Clara

Hello!

The best is to practice, practice, practice! I could recommend you to start with:

1. GMAT exams: that can be found for free in the internet (GMAT prep with The Economist, London Business School free trial, etc.)

2. Math tools: such as Mimir math for iOS or Math tool on Viktor Cheng´s website)

3. Multiplying any two 2 digit number in 3 seconds: check this great video > https://www.youtube.com/watch?v=6ndkkPZYJHo

Best,

Clara

Book a coaching with Antonello

98% Recommendation Rate

169 Meetings

6,656 Q&A Upvotes

USD 219 / Coaching

Book a coaching with Vlad

98% Recommendation Rate

413 Meetings

11,464 Q&A Upvotes

USD 239 / Coaching

Hi,

First of all, I recommend using the following approach while doing your calculations

  1. Tell the interviewer your approach / formula

  2. Check with the interviewer that your approach is correct

  3. Ask for a minute to perform the calculations

  4. Check any assumptions you make with the interviewer. If you need to round the number - you have to check with the interviewer as well

  5. Come to the interviewer with some intermediate calculations results to check that you are moving in the right direction

  6. Come up with the final answer

  7. Provide the conclusions from the final answer

The following skills will speed up your calculations and reduce the probability of making a mistake:

1) Learn how to solve equations and systems of equations. As you could have noticed, some cases require solving an equation. You can use GMAT books to practice.

2) Learn how to multiply double-digit numbers really fast. It takes just a couple of hours to learn how to apply this method on paper and a couple of days to start doing these calculations mentally, but it's worth it. Please follow the link for more details: https://www.youtube.com/watch?v=6ndkkPZYJHo

3) Learn how to work with zeros.

Simply always use the powers of 10. Then you'll be able to multiply / divide the numbers and sum up / subtract the powers separately:

For example: 300 x 9000 = 3 x 10ˆ2 x 9 x 10ˆ3 = 3 x 9 x 10ˆ(2+3) = 27 x 10ˆ5 or 2.7 Mln

If you get used to writing all the numbers that way, you will never lose zeros.

4) Learn the division table. This method will help you calculate any percentage problems like market shares or margins. For example, if your market is $620M and your revenues are $5.1M you can use 5/6 or 83.3%, as a proxy to calculate the market share. By adjusting to zeroes and slightly decreasing the number, you'll get 8.2%

Best!

Hi,

First of all, I recommend using the following approach while doing your calculations

  1. Tell the interviewer your approach / formula

  2. Check with the interviewer that your approach is correct

  3. Ask for a minute to perform the calculations

  4. Check any assumptions you make with the interviewer. If you need to round the number - you have to check with the interviewer as well

  5. Come to the interviewer with some intermediate calculations results to check that you are moving in the right direction

  6. Come up with the final answer

  7. Provide the conclusions from the final answer

The following skills will speed up your calculations and reduce the probability of making a mistake:

1) Learn how to solve equations and systems of equations. As you could have noticed, some cases require solving an equation. You can use GMAT books to practice.

2) Learn how to multiply double-digit numbers really fast. It takes just a couple of hours to learn how to apply this method on paper and a couple of days to start doing these calculations mentally, but it's worth it. Please follow the link for more details: https://www.youtube.com/watch?v=6ndkkPZYJHo

3) Learn how to work with zeros.

Simply always use the powers of 10. Then you'll be able to multiply / divide the numbers and sum up / subtract the powers separately:

For example: 300 x 9000 = 3 x 10ˆ2 x 9 x 10ˆ3 = 3 x 9 x 10ˆ(2+3) = 27 x 10ˆ5 or 2.7 Mln

If you get used to writing all the numbers that way, you will never lose zeros.

4) Learn the division table. This method will help you calculate any percentage problems like market shares or margins. For example, if your market is $620M and your revenues are $5.1M you can use 5/6 or 83.3%, as a proxy to calculate the market share. By adjusting to zeroes and slightly decreasing the number, you'll get 8.2%

Best!

Dear Isabel!

For practicing and improving your mental math you can find also some apps and tools, besides Victor Cheng’s math tool (Magoosh's mental maths app, Mental math cards challenge app, etc). But there are some facts that will help in overall improvements:

Consulting math is very different than academic math. Working consultants - and consulting interview candidates - are always under time pressure. Results are what matter and answers are required simply to be good enough to guide business decisions, rather than being absolutely correct.

The next important thing is that rather make it on the paper to structure the notes and then to communicate the results clearly rather than make your calculations fast

The time pressure in case interviews is severe and you cannot afford to waste time. But to make your calculations right you shouldn’t be in a rush. So, I would recommend you here to work on both - practice with time limitations and learn how to keep your mind peaceful and concentrated (it might be not so popular advice here, but mediations really make their job here ).

Be comfortable and confident to state your answers, not as a question. Interviewers notice this, and this will not give credit.

If you need any further help or career advice, feel free to reach me out.

Best,

André

Dear Isabel!

For practicing and improving your mental math you can find also some apps and tools, besides Victor Cheng’s math tool (Magoosh's mental maths app, Mental math cards challenge app, etc). But there are some facts that will help in overall improvements:

Consulting math is very different than academic math. Working consultants - and consulting interview candidates - are always under time pressure. Results are what matter and answers are required simply to be good enough to guide business decisions, rather than being absolutely correct.

The next important thing is that rather make it on the paper to structure the notes and then to communicate the results clearly rather than make your calculations fast

The time pressure in case interviews is severe and you cannot afford to waste time. But to make your calculations right you shouldn’t be in a rush. So, I would recommend you here to work on both - practice with time limitations and learn how to keep your mind peaceful and concentrated (it might be not so popular advice here, but mediations really make their job here ).

Be comfortable and confident to state your answers, not as a question. Interviewers notice this, and this will not give credit.

If you need any further help or career advice, feel free to reach me out.

Best,

André

Related case(s)

MBB Final Round Case - Smart Education

Solved 18.7k times
MBB Final Round Case - Smart Education Our client is SmartBridge, a nonprofit educational institution offering face-to-face tutoring services. The client operates in the US. The mission of SmartBridge is to help as many students as possible to complete studies and prevent that they drop from the school system, in particular in disadvantaged areas. The client is considering starting operations for its services in the Chicago area. They hired us to understand if that makes sense. Due to the nonprofit regulation, SmartBridge should operate on its own in the market, without any partnership. How would you help our client?
4.6 5 649
| Rating: (4.6 / 5.0)

Our client is SmartBridge, a nonprofit educational institution offering face-to-face tutoring services. The client operates in the US. The mission of SmartBridge is to help as many students as possible to complete studies and prevent that they drop from the school system, in particular in disadvant ... Open whole case

Coronavirus Times - COVID-19 Brainteaser

Solved 3.5k times
Coronavirus Times - COVID-19 Brainteaser You and your family are faced with a challenging set of decisions. Due to coronavirus, your partner has taken a 20% paycut and you are worried you may lose your job. In addition, while daycare is still open, you are worried that sending your two children there will increase the risk of them bringing the virus back to your house, where your elderly grandparents are also staying. How would you go about thinking about this problem, and what would you recommend?
4.6 5 37
| Rating: (4.6 / 5.0)
Difficulty: Beginner | Style: Brain Teaser | Topics: Brain teaser

You and your family are faced with a challenging set of decisions. Due to coronavirus, your partner has taken a 20% paycut and you are worried you may lose your job. In addition, while daycare is still open, you are worried that sending your two children there will increase the risk of them bringing ... Open whole case

Bain 1st Round Case – BlissOttica

Solved 2.7k times
Bain 1st Round Case – BlissOttica Our client is a BlissOttica, an Eyewear Manufacturer that is looking to reach a 10% increase in profits. How would you help our client?
4.3 5 130
| Rating: (4.3 / 5.0)

Our client is a BlissOttica, an Eyewear Manufacturer that is looking to reach a 10% increase in profits. How would you help our client? Open whole case

Cutting Carbs - Divestiture in the Electrical Power Market

Solved 2.2k times
Cutting Carbs - Divestiture in the Electrical Power Market Our client is Energy England, one of northern England’s largest electric utility companies. They were created over the past decade through an aggressive series of mergers of existing utility companies each specializing in a single energy generation source. Recently, the CEO has embarked on an initiative to return to the core of the business. She is looking to increase free cash flow and cash reserves in order to prepare the business for evolving future trends.   The following can be verbally provided to interviewee if asked: Energy England is made up of assets across the energy-generation space. These include coal, gas, nuclear, and wind We are looking to divest from just one of our previous acquisitions (i.e one target is sufficient) There are no specific goals/metrics – the client trusts our judgement
4.3 5 45
| Rating: (4.3 / 5.0)

Our client is Energy England, one of northern England’s largest electric utility companies. They were created over the past decade through an aggressive series of mergers of existing utility companies each specializing in a single energy generation source. Recently, the CEO has embarked on an initi ... Open whole case

Cats in the Berlin Olympic Stadium

Solved 600+ times
Cats in the Berlin Olympic Stadium An American marketing company plans to fill the Olympic Stadium in Berlin with cats for an advertising event and now hires your consulting company to find out how many animals they would need for this.
4.0 5 6
| Rating: (4.0 / 5.0)

An American marketing company plans to fill the Olympic Stadium in Berlin with cats for an advertising event and now hires your consulting company to find out how many animals they would need for this. Open whole case