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Leveraged Breakdowns

Brain Teasers in Real Estate Private Equity Interviews


Brain teasers are an important topic in our coverage of real estate private equity for beginners. They show up quite often during interviews, though they may not always touch upon real estate-specific concepts. Categorically, they’re not the same as the other technical questions in our comprehensive guide. In fact, I consider brain teasers to be behavioral questions.

Like the other behaviorals we’ve been covering in this series, the purpose of brain teasers is more geared toward exposing how you think and behave. This is different from technical questions, which probe your mastery of a defined subset of factual and formulaic knowledge.

The following post will teach you how to appropriately respond to a brain teaser. Break it down into variables, estimate those variables, then string them together to generate a formulaic output. Keep reading for specifics!

How many piano tuners are in Chicago?

What if, in your next real estate private equity interview, you encounter the following brain teaser: how many piano tuners are in Chicago? Of course, you could Google the answer. But this is an interview, they don’t really care what the answer is. Instead, your interviewer is screening to see whether you are a thoughtful individual. So, how should you respond?

Show, Don’t Tell

Remember when the middle school math teacher made you show your work on homework and quizzes? Even if you knew the answer, you would lose points if you didn’t show your work. That’s exactly what’s going on here. The interviewer wants to hear the following:

  1. Subdivide this problem into several variables (3 or 4 minimum, more if you’re capable under stress)
  2. Assign values to those individual variables
  3. Verbally walk those variables through a formula that outputs an estimate

The interviewer wants to hear all of that. You should never just spit out an answer without showing any thought, even if you’re absolutely correct. But feel free to ask if they’d like you to use paper and a pencil to track your variables (ask like it’s a convenience for them). This advantage could help.

Estimating Chicago’s Piano Tuning Population

Let’s walk through the aforementioned brainteaser, which is in fact a famous example favored by physicist Enrico Fermi. How many piano tuners are in Chicago?

Chicago’s population is roughly 3 million. If the average household contains four members, there’s likely 750,000 families. If one in five families owns a piano, you’d expect about 150,000 pianos in Chicago. If a tuner can service four pianos every day, works five days per week, and vacations two weeks during the summer, then in one year the tuner would service 1,000 pianos. If a piano needs servicing once per year, that’d imply about 150 piano tuners (150,000 estimated pianos divided by the annual rate of 1,000 pianos serviced per tuner).


With brain teasers, the goal is not to output a correct result. You’re seeking to establish a guesstimate that is likely accurate within a factor of perhaps 2 or 3, certainly 10. But even more important is your interviewer’s focus on your approach. Bad inputs can be fixed – it’s more important to show that you know how to isolate key factors when facing an unknown problem.

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