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Overview

Once you’ve been invited for an interview, it’s important to prepare yourself with a game plan. Most consulting interviews are different from regular job interviews because they involve case studies and questions that require more than just your qualifications. You’ll want to be prepared to answer quantitative and qualitative questions about the market size of product X or what it will take for project Y to succeed. This article offers key points on how to do that in order to get the job offer you’re looking for.

In this article, you’ll learn how to do complex arithmetic calculations quickly and precisely. You’ll also find out when it’s useful to use a proxy, and why you should expect your interviewer may be aggressive.

Big Idea #1: Even if you are a world champion mathlete, you’ll need to practice hard for your interview.

Have you ever interviewed with a consulting firm? If so, you know that the interview will involve solving business challenges. These are called case interviews and they usually include quantitative questions.

The first type of question is a math problem, which involves some sort of arithmetic or percentage calculation. An example would be “if the total innovation capital for company A is $X and it grows at five percent per year, what needs to happen for the firm to represent more than half of the total innovation capital within ten years?”

Math is a subject that can be tough. It requires practice to excel at it, just like any other skill. Even if you’re good with math, your brain needs regular exercise to perform optimally in this area.

Even though some people get high marks in their math classes, they can still fail at the SAT (Scholastic Assessment Test) if they don’t practice enough. Therefore, it’s important to do regular drills that improve your speed and confidence.

One way to get better at interviews is to practice old questions. For example, by searching for the types of questions asked in a McKinsey or Boston Consulting Group interview, you’ll be able to automate your responses and answer those types of questions quickly.

But be aware that the test is always changing, so you need to get updated tests.

Now that you know how to solve math problems, it’s time to learn about the second type of quantitative problem: computational-level estimates.

Big Idea #2: Complicated problems can be solved quickly by breaking them down and using rounding.

Computational questions are problems that require you to perform complex arithmetic using large numbers. Such questions can be answered precisely and quickly if they’re broken up into smaller parts. For instance, you might be asked: “You have a market of 3 million customers, assume a 15 percent market share and revenue of $200 per customer. What is your total revenue?” To break this down, first find the total value of the market which is 3 million buyers x $200 = $600 million. Then, to calculate 15 percent of 600 million, you can break it into 10 percent and 5 percent to find that 10 percent of 600 million = 60 million and 5 percent of 600 money = 30 million. Now all you’ve got to do is simple addition: 60 + 30 = 90

But it’s not always necessary to get an exact number. In fact, you can make a rough estimate of something without getting the precise value. You simply need to round numbers so that you can perform calculations more quickly and easily.

So, take a variation of the previous question in which you have 42 million customers and 12.7 percent market share. What is the total revenue?

We can’t find the answer to this problem quickly in our heads, so we need to be as precise as possible. If we round 42 million buyers down to 40 million and then round 12.7% up to 15%, we’ll get a close approximation of the correct answer: $1.2 billion in revenue, which is much better than guessing wildly at an answer or using a calculator for something that’s simple math anyway!