Many case interview preparation resources have example calculations that you are highly unlikely to encounter in an actual case interview, such as multiplying by a number like 23,487, which has five significant digits and no clear way to simplify the calculation. These numbers are representative of actual Case Numbers, and most actual multiplication calculations in case interviews involve numbers like 25,000 or 25 Million, for which there is a way to dramatically simplify the calculation. Using this method relies on the fact that 25 = ¼ × 100. This method works because (4 × 25 = 100) so, when you divide 32 by 4, the result is the “number of groups of 100.” Now the answer to our original problem of ($32 × 25,000) is then $800,000. So to multiply any number by 25, you divide the number by 4 and then multiply by 100. Now a quarter is also worth 25 cents, and since we have 32 quarters, then 32 × 25 = 800. So 32 quarters make $8, which is 800 cents.
The answer is clearly 800: (8 × 100 = 800), as there are 100 cents in 1 dollar. Now think about how many cents are in $8. coins) how much money would you have? You might think to yourself: “Well, 4 quarters make 1 dollar, and 32 ÷ 4 = 8, so I would have $8,” which is correct. You can think of this new calculation method as follows: let’s say you are given 32 quarters (U.S. Therefore (32 × 25 = 800) - you can check this with a calculator or pen-and-paper calculation. Then we perform the calculation using this decomposition of 25. These numbers are representative of actual Case Numbers, and here is an efficient method for this calculation (32 × 25). You can make the pen-and-paper calculation more efficient by not writing out the three zeroes from “25,000” and then adding them to the end of the result of (32 × 25). Most people would use pen and paper for this calculation. You would then need to do the calculation: ($32 × 25,000). For example, let’s say you are told a company sells a product for $32 per unit and sells 25,000 units per year, and you are asked to calculate the revenue. When Case Numbers have more than one significant digit, they usually have additional properties that can make certain calculations like multiplication and division much easier if you are aware of the appropriate methods.
While some people may be intimidated by having to do calculations with large numbers like this without a calculator, once you learn how to efficiently manage the zeroes, calculations with numbers like these become straightforward.
All the Case Calculations take this into account, so Case Numbers and Case Calculations usually have certain characteristics you can use to simplify the calculations (if you are familiar with certain calculation methods).įor example, Case Numbers are usually round numbers with only a few significant digits, such as 300,000 or 4,000,000. As a reminder, candidates cannot use calculators or spreadsheets in the case interviews but may use pen and paper. The best way to prepare for the quantitative portion of case interviews is to practice the types of calculations you will need to perform with numbers representative of actual Case Numbers and to be familiar with the types of problems you are most likely to encounter and how to solve them.
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