1. 100% Recommend Rocket Blocks. It's exactly what you're looking for
2. Online "Drills": https://www.preplounge.com/en/mental-math
3. Math sheets (print these and do them on paper): Google Math Drills sheets
4. 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 formulas/concepts:

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

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

Mental Math

https://www.preplounge.com/en/consulting-forum/mental-math-help-7962

Conceptual/Contextual Math

https://www.preplounge.com/en/consulting-forum/materials-for-practicing-conceptual-case-math-8016

Key Math Equations

https://www.preplounge.com/en/consulting-forum/math-equations-their-use-7934

Hi there,

My advice is to start using Preplounge's mental math tool, which you can find here: Mental Math Practice | PrepLounge.com. You will find your own shortcuts with time for basic arithmetic operations. However, execution is only 1 part of 4 important parts for quant:

1. When to do math: It isn't always obvious when to crunch some numbers to create insights when you're not being asked directly. Most people miss opportunities to score some points because they're not proactive in the right moments.
2. Setting up an equation: Sometimes it's not as easy as adding x + y and you might have to solve for variables with a more complex approach. Knowing what to solve for and how to do it comes before execution and is extremely important.
3. Doing the math (what you asked about): Once you know what you want to do and how to do it, it's time to actually do it. It's important to be reasonably quick and “right enough”. The latter refers to the liberty you can take to sometimes approximate numbers, rather than getting the decimals right. With practice you'll get a feeling for how precise you need to be, which determines complexity and length of the entire execution part.
4. Contextualizing result: Spitting out a number is not enough. You must contextualize it to create the right insights. A lot of candidates forget this and focus too much on answering the question right, rather than doing something with that right answer. This is not necesarily a quant skill and is more attributable to conceptual skills. Nonetheless, a very important thing to get right. If you don't, all previous steps are devalued.

I am happy to help with all the above, if that's needed.

Best of luck!

Moritz

I understand that mental math can be challenging, especially when you're aiming for precise calculations. Fortunately, there are several resources available to help you improve your mental math skills.

For useful tricks and tips, I recommend checking out the following:

PrepLounge's Mental Math Drills: This online resource provides practice exercises specifically designed to improve mental math skills. You can find it here: [https://www.preplounge.com/en/mental-math]

Rocket Blocks: Rocket Blocks is a comprehensive platform that offers case interview preparation, including mental math drills. It provides step-by-step guidance and practice materials. You can learn more about it here: [https://www.rocketblocks.me/]

Google Math Drills Sheets: These printable math sheets can be a great way to practice mental math on paper. You can find a variety of math drills by searching for "Google Math Drills Sheets."

In terms of formulas commonly used in case interviews, here are a few examples:

Breakeven Point: This formula helps determine the point at which a company's revenue equals its costs, resulting in neither profit nor loss.

Return on Investment (ROI): ROI measures the profitability of an investment by comparing the gain or loss relative to the cost of the investment.

Net Present Value (NPV): NPV calculates the present value of future cash flows, taking into account the time value of money.

While these are just a few examples, it's important to familiarize yourself with a wide range of formulas and concepts. You can find more information on case math and commonly used formulas in the "Case Interview Math" section of PrepLounge's resources.

I hope these resources and tips help you improve your mental math skills and feel more confident in case interviews. Good luck with your preparation!

Hi,

Plenty of websites that can give you tips on mental arithmetic - a google search will show these.

For me, I found the book “Secrets of Mental Math” to be helpful - especially the mnemonic section was extremely helpful on the job.

All the best!  

Hi there!

Yes - for speed, use Arithmetic Zetamac. 

For logic, reach out to me and I'll send you a guide over DMs (no strings attached). 

For terms, check out the guide I created:

• Expert Guide: The Must-Know Consulting Terms for Interviews

Best,
Cristian

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