- Introduction: Overview and Background
Introduction & Background
This section discusses Case Interviews in general and how the qunatitative component of Case Interviews fits into the entire interview. It also has an example of a full Case Interview.
Context of Quant Problems in Case Interviews
This lesson discusses the context of quant problems in Case Interviews and why consulting firms assess quant skills
Math Skills Required for Case Interviews
Course Requirements and Math Review (Optional)
McKinsey Full Case: Catalog Retailer
This is an example of a full McKinsey Case Interview and includes recommended answers for all phases of the interview
BCG Full Case Example
- FastMath: Multiplication and Division Methods
Division & Factoring 1
FastMath methods for division and factoring numbers
Division & Factoring 2
FastMath Practice Problems
Mental Math Regular Exercises
- Detail: Multiplication & Division Methods
Multiplying & Dividing by 25
Multiplying & Dividing by 5 & 50
Handling Zeroes I
Handling Zeroes II
Mult. & Div. by 2 Part I
Mult. & Div by 2 Part II
- FastMath: Percentage Growth/Change
Compound Growth 1
Compound Growth 2
Compound Growth 3
Doubling (& Halving) Time
- Market Sizing & Estimation Problems
Example 1: McDonald's US Sales
Example 2: US Auto Sales
Market Sizing Practice Problems
- Quant Case Problems
Simple Profitability & Breakeven Analysis
Response Rate Analysis
Economies of Scale
Growth Rate Analysis
Chart Reading 1
Chart Reading 2 (Recommended)
Investment Decision (Full Case)
Hard: Production Shifting (McKinsey)
Competitive Pricing Response
Hard: Pipeline Analysis (McKinsey)
Pipeline Analysis: Algebraic Solution
McK Organ Donation Case
Summary & Conclusion
- Advanced Quant Topics
NPV 1: Net Present Value Overview
NPV 2: Perpetuities & Examples
Accurate Compound Growth Calculations (McK PST)
NPV 3: Perpetuities with Growth
NPV 4: Sensitivity Analysis
- McKinsey PST Materials
Practice Test A: Kosher Franks
Practice Test B: Freddie's Shrimp
PST Tips & FastMath Methods
Solutions to Practice Test A
Solutions to Practice Test B
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FastMath Ace the Case
Ace the Quant Component of Case Interviews!
The World's #1 Selling Online Course for Case Interview Math
Learn quantitative skills for Case Interviews
from a former McKinsey consultant
See our new web site at: www.fastmath.net
Online Course Features
Trusted by Students from
Hello! My name is Matthew Tambiah and I’m the creator of the FastMath Ace the Case Online Course. I’m a former McKinsey consultant and a graduate of both Harvard and MIT, and I designed this video-based online course specifically to teach you the quantitative and mental calculation skills you need to succeed in Management Consulting Case Interviews.
Since you can't use calculators during Case Interviews, many people are nervous about the quantitative component of Case Interviews. However, math has always come naturally to me. I excelled in math starting in elementary school and continuing through college at Harvard and graduate school at MIT. In this online course, I will teach you the quantitative and mental calculation methods I personally used to successfully navigate the McKinsey Case Interview process. I have used similar methods throughout my academic career, and these methods helped me earn top scores on standardized tests such as the SAT and the GMAT, and to be admitted to — and excel academically at — both Harvard and MIT.
Email me at: email@example.com
Why Quant Skills Are Important in Case Interviews
Case Interviews require candidates to perform mathematical and quantitative analysis, interpret results, and develop insights and recommendations — all without using a calculator or spreadsheet, which many people find very challenging and/or intimidating. The pressure is further compounded by the fact that, as your quant evaluation is a critical factor in your overall evaluation as a candidate, a high paying job and your future career are at stake — so performing poorly can sink your chances of receiving an offer.
Management consulting firms assess the quant skills because of candidates because — as clients hire management consultants primarily to provide recommendations based on objective quantitative data and analysis — effective management consultants need strong quantitative skills. A firm's assessment of your quant skills carries strong weight in its hiring decision — the quant assessment typically contributes 20–25% of the overall candidate evaluation. Many firms do have a minimum bar for quant skills and you are unlikely to receive an offer if your performance is under that bar. One great way to distinguish yourself from other candidates is to demonstrate outstanding quantitative skills.
Read the articles below for more detail on why firms assess quant skills — as well as the specific quant skills assessed in Case Interviews.
Articles: Why Quant Skills are Important in Case Interviews
In the FastMath Ace the Case Online Course, I use on-demand video instruction to teach calculation methods designed specifically to simplify the types of calculations required in Case Interviews at elite Management Consulting firms such as McKinsey, Bain and BCG. These FastMath calculation methods will make you faster and more efficient — and reduce your calculation errors — by drastically simplifying most Case Interview calculations (Case Calculations). I will then show you how to apply these FastMath calculation methods to the most common types of Case Interview quantitative problems, such as Market Sizing & Estimation problems, Break-even Analysis problems, and Price Optimization problems.
The FastMath Ace the Case Online Course is the quant Case Interview preparation resource recommended by the consulting clubs at Wharton, Columbia Business School, London Business School and numerous other MBA programs. More than 5,000 candidates worldwide have used the FastMath Ace the Case Online Course to prepare for Management Consulting interviews. Discover why top MBA students love FastMath, and maximize your own interview performance by registering for the FastMath Ace the Case Online Course.
You can preview several lessons — see the blue links on the right.
FastMath Ace the Case Differentiators
The FastMath Ace the Case Online Course is different from other quantitative interview-preparation resources because I use on-demand video lessons to teach you how to do Case Calculations faster and more efficiently. Most other quantitative interview-prep resources simply provide practice problems and answers — without teaching methods to efficiently perform the calculations without a calculator.
Furthermore, all the calculation methods in this course are designed specifically for the types of calculations you will actually encounter in a Case Interview, and all the example problems are based on problems given in actual Case Interviews at elite Management Consulting firms. I also cover efficient solution methods to a wide variety of the most common types of quant Case Interview problems. Many other quant interview-prep resources use examples that don't reflect actual Case Interview problems and don’t cover the full range of calculation types and problem types that I cover in .
For example, most numbers used in Case Interviews (what I call Case Numbers) are either “round” numbers like 2,000,000 or have specific characteristics you can use to simplify calculations with those numbers — if you know the proper methods! In the FastMath Ace the Case Online Course, I focus on teaching efficient methods for doing the calculations in Case Interviews with actual Case Numbers. See this page to learn more about how this course was Designed for Real Case Calculations.
The FastMath Ace the Case Online Course has two main components. In the first half I will teach you a set of FastMath calculation methods that will enable you to do multiplication, division, percentage and compound growth calculations faster and more efficiently without a calculator — as required in Case Interviews. In the second half, I’ll show you how to apply the FastMath calculation methods to the most common types of quantitative problems given in case interviews, such as Market Sizing & Estimation problems and Break-even Analysis problems. I will illustrate the most efficient solution method for each problem type, and show how to use the FastMath calculation methods to solve the problems quickly and efficiently. I will also highlight how to use the quantitative results to develop Case insights and recommendations. I’ll provide you with numerous full Case Interview example quant problems with detailed solution methods, and comprehensive practice problems and solution methods that reinforce the course material. I have also included some materials useful in preparing for the McKinsey PST.
Mental Calculation Methods
Quant Problem Types
30-day Money-back Guarantee
If you're not satisfied with this course for any reason, email me and I will provide a refund.
Designed for Real Case Calculations
Before I created this course, I looked at numerous quantitative problems that top Management Consulting firms like McKinsey, Bain, BCG, Accenture and Deloitte had given to their candidates in Case Interviews. I then created the course content to teach people the most effective ways to solve the actual problem types elite Management Consulting firms were asking candidates to solve.
By looking at the actual calculations required in Case Interview, I also noticed that the specific numbers involved in the Case Calculations, which I will refer to as Case Numbers, had specific properties you could use to simplify the calculations — if you knew the proper methods. The Case Numbers showed signs of being carefully chosen, and the calculation methods I teach in the FastMath Ace the Case Online Course are designed specifically for the actual calculations required in Case Interviews.
Case Numbers are usually “Round” numbers with a few significant digits, such as 300,000 or 4,000,000. Some people may be intimidated by having to do a calculation like (4,000,000 × 20,000) without a calculator. In this course, I’ll teach you efficient methods to manage the zeroes (see Multiplication Lesson), so that calculations like these will become easy. When Case Numbers have more than one significant digit, they usually have certain characteristics that can make calculations like multiplication and division much easier.
Example Case Calculation
You are told that a company sells a Product for $32 per unit and sells 25,000 units per year, and then you are asked to calculate the Revenue.These numbers are representative of actual Case Numbers, and you would need to do the calculation: ($32 × 25,000). You can execute this calculation by multiplying (32 × 25) and then writing the three zeroes from “25,000” at the end of this result. Here is a way to efficiently perform the calculation (32 × 25) using relevant characteristics of these Case Numbers.
First, decompose 25 as (25 = ¼ × 100) — then perform the calculation using this decomposition of 25.
32 × ¼ = 32 ÷ 4 = 8
8 × 100 = 800
Therefore (32 × 25 = 800). You can (and should) verify this with a calculator or pen and paper. This method works because (25 = ¼ × 100), and so (4 × 25 = 100); so, when you divide 32 by 4, the result is the “number of groups of 100.” In general, to multiply any number N by 25, you divide N by 4, and then multiply the result by 100. Now the answer to our original problem of ($32 × 25,000) is then $800,000.
Most multiplication and division calculations required in actual Case Interviews involve numbers like this for which there is a way to dramatically simplify the calculation. In the Fastmath Ace the Case Online Course, I’ll provide you with a comprehensive set of methods for multiplying and dividing with the Case Numbers you are most likely to encounter in actual Case Interviews.
Beware of “Imposter” Case Calculations
Many other quantitative Case Interview preparation resources have example calculations with Case Numbers you are highly unlikely to encounter in an actual Case Interview, such as multiplying by a number like 23,487 — or a number with five (or more, significant digits. Practicing calculations with numbers with many significant digits is not an effective way to prepare for Case interviews as these calculations are not representative of actual Case Numbers or Case Calculations. You will be practicing brute-force mechanical calculation skills which you won’t need in Case Interviews, and won’t get experience looking for and finding methods to simplify calculations.
If you see example problems where you are multiplying or dividing by numbers with four or more significant digits, or adding numbers with five or more significant digits, this is a red flag indicating these calculations are likely “made up” and not representative of actual Case Numbers and Case Calculations. As a result, there are no longer efficient methods to perform the calculation — and practicing with these types of problems is not an effective way to prepare for actual Case Interviews.
All the calculation methods, example problems, and practice problems in the FastMath Ace the Case Online Course are based on actual Case Calculations (and the specific Case Numbers involved) from leading management consulting firms like McKinsey, Bain, BCG, Accenture and Deloitte. Therefore, I believe the FastMath Ace the Case Online Course is the best quantitive Case Interview preparation resource because it will prepare you for the types of problems you are actually likely to encounter in a Case Interview.
Quant Self-diagnostic Quiz
For a quick assessment of your quant skills, take the FastMath Ace the Case Quant Self-diagnostic Quiz, and score yourself using the Solutions and Scoring Guidelines. The results will highlight areas for improvement.
Mental Math Exercises
Former McKinsey Consultant
- Bachelor's from Harvard with Highest Honors in Electrical & Computer Engineering.
- MBA from MIT Sloan
I am the creator of the FastMath Ace the Case Online Course. I have taught FastMath Ace the Case Workshops at Harvard Business School, Wharton, MIT, London Business School, INSEAD, Georgetown and numerous other leading universities. Thousands of candidates from around the world have used the FastMath Ace the Case Online Course to prepare for Case Interviews. My students have joined McKinsey, Bain, BCG, PwC, Accenture, Deloitte, Booze Allen, and other leading consulting firms. I have a Bachelor's degree from Harvard with Highest Honors in Electrical and Computer Engineering. Before I attended the MBA program at MIT, I worked at Akamai Technologies, a leading computer networking firm, in both Silicon Valley and Cambridge, Massachusetts, in sales engineering, product management and product marketing roles.
Math and science subjects always came naturally to me and I frequently helped friends with these subjects in high school, in college at Harvard, and in graduate school at MIT. I have received the following scores on math and science standardized tests
- Math SAT: 800/800
- GMAT: 99th percentile
- Advanced Placement BC Calculus: 5/5
- Advanced Placement Physics C Mechanics: 5/5
- SAT Mathematics Level 2 Subject Test: 800/800 (formerly the SAT Math II Achievement test)
I developed the concept for the FastMath Ace the Case Online Course when I was in business school at MIT. I was enrolled in the 2-year MBA program at MIT, and I spent the summer between the first and second year working in the technology practice at McKinsey. When I returned to school in the fall of my second year, many classmates asked me to help them prepare for their Case Interviews because I had successfully navigated the process. I started giving people some of the Case Interview questions I received, and noticed that many people struggled with the quant problems — even people with strong math and science backgrounds. There were many Case Interview preparation resources, but I didn't think they did a good job helping people prepare for the quantitative component of Case Interviews, so I volunteered to host a workshop on quant skills for Case Interviews for MIT students through MIT Sloan Management Consulting Club. My classmates likes the material and this was the inspiration for the current version of the FastMath Ace the Case Online Course.