My Take on Brainteaser Interview Questions in 2024

Some practical advice for those facing them for the first time

Aug 17, 2024

Brainteasers in job interviews—just hearing the word brings back a flood of memories from my own career journey.

I was recently scrolling through LinkedIn when I came across a couple of posts [1][2] about these classic riddles. Questions such as calculating the angle between clock hands, or figuring out the odds of drawing two aces in a row. Turns out, Goldman Sachs is still using these in their interviews!

This got me thinking (my fortuitous thought). Google ditched these types of questions over a decade ago [3], deciding they weren’t the best predictors of job performance.

So, why are these brainteasers making a comeback? Or maybe the better question is: did investment banks like Goldman Sachs ever really stop using them? Did other tech firms such as Microsoft ditch them when Google did? 🤔

Having been through the interview gauntlet multiple times, I thought I'd share my insights and offer some practical advice, especially for those newer to the job market. I’ve also included a small worked example on the piano tuner question.

The Monty Hall Problem: My Personal Experience

I’ll share a personal story that still makes me sweat a little whenever I think about it. I was once asked the Monty Hall problem during an interview, and if you’ve ever encountered it, you’ll know it’s one of those puzzles that can really throw you for a loop.

If you are unfamiliar with it, the Monty Hall problem goes like this: You’re on a game show and asked to choose one of three doors. Behind one door is a car, and behind the other two are goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?"

Is it to your advantage to switch your choice?

Most people think it doesn’t matter if they switch or stay because the odds are now 50/50. But here’s the thing: probability theory actually tells us you double your chances of winning by switching doors (from 1/3 to 2/3)!! 😲

Thankfully, this was one of the questions I’d reviewed during my prep, so I could (somewhat) confidently reason aloud and work out the answer.

But this experience really highlighted why brainteasers are so valuable in interviews. They’re not just about getting the right answer, but about showing your reasoning process and how you handle unexpected twists.

My Practical Advice for Zoomers and Job Seekers

For those of you who are just starting out in your careers and might be facing these brainteasers for the first time, I have some practical advice that should help you (they helped me in my time):

Understand the Purpose: These questions are designed to test your problem-solving skills and how you think, not necessarily to get a "correct" answer.
Understand the Types of Brainteasers: These puzzles usually fall into categories like probability, geometry, logic, or Fermi estimates (such as estimating how many tennis balls can fit in a Boeing 747). Knowing what to expect can help you stay calm when one gets thrown your way.
Use Structured Thinking: Break down complex problems into smaller, manageable parts and tackle it step by step. Even if you don’t nail the answer, demonstrating clear thinking under pressure is often enough to impress. Also, this is a skill that will serve you well beyond just interviews!!
Learn from the Classics: Some of these brainteasers have been around for decades and are still relevant today. Books like "Heard on the Street" [4] for finance questions and "How Would You Move Mt. Fuji?" [5] for general brainteasers were my go-to resources back in the day. They’re great for getting a feel for how to approach these problems.
Practice, Practice, Practice: There’s really no substitute for preparation. The more you practice, the more comfortable you’ll be with the format. Don’t just focus on finding the right answer, focus on how you get there. Be able to explain your thought process aloud while you work through the problem.
Think Out Loud: In an interview, it’s not just about what you know, it’s about how you think. When faced with a brainteaser, take your time and talk through your reasoning. This shows the interviewer that you can approach problems methodically and logically.
Don't Be Afraid to Ask Questions: If something isn't clear, ask for clarification. At the very least, its shows you're engaged and thorough.
Stay Calm and Composed: Brainteasers are designed to test how you perform under pressure. Take a deep breath. How you handle the pressure is at least as important as getting the answer.
Embrace the Learning Opportunity: If you get stumped by a brainteaser during an interview, don’t get discouraged. Take it as a learning opportunity. Look up the question afterward and figure out where you went wrong. This will make you better prepared for the next time.
It's a Two-Way Street: These questions also give you an insight into the company culture. Consider if this is the type of environment where you'd want to work, and whether you would do well there.

A Step-by-Step Approach: The Piano Tuner Problem

Let me walk you through how I'd approach a classic brainteaser: "How many piano tuners are there in Chicago?"

Here's my thought process:

Start with what I know: Chicago's population is roughly 2.7 million. If I didn’t know this, I’d make reasonable assumptions based on what I did know and say it out loud.

For example: “I know that Chicago is the 3^rd most populous city in the US behind New York and LA. The New York population is about 8.3 million, hence a reasonable number for Chicago is 3 million”.

Make further reasonable assumptions:
- Maybe 1 in 20 households has a piano (5%)
- Average household size is about 2.5 people
- Pianos might need tuning once a year
- A piano tuner might tune 4 pianos a day, 5 days a week, 50 weeks a year
Do the maths:
- Number of households: 2,700,000 / 2.5 = 1,080,000
- Number of pianos: 1,080,000 * 5% = 54,000
- Pianos tuned per year per tuner: 4 * 5 * 50 = 1,000
- Number of piano tuners: 54,000 / 1,000 = 54

So, I might estimate there are around 50-60 piano tuners in Chicago.

The important thing is not the exact answer (the interviewer probably doesn’t know either!), but demonstrating logical thinking, making reasonable assumptions, and clearly explaining your thought process.

Opening the Conversation: A Trip Down Memory Lane

I vividly remember the 90s and early 2000s when these types of questions were all the rage, especially at investment banks and tech giants. I faced dozens of these across various interviews, each one testing my problem-solving skills, creativity, and ability to think under serious pressure.

So, why is Goldman Sachs seemingly bringing them back? It's a question that's been nagging at me. Have brainteasers really made a comeback, or did they never really leave the investment banking scene?

I’d love to hear from others who’ve experienced this at their interviews. Have you come across these questions in recent interviews (2020s)? Do you think they’re still relevant, or are they a relic of the past?

Let’s start a conversation. Share your thoughts, experiences, and any brainteasers that have stumped you along the way in the comments below!

The Enduring Value of Brainteasers

So, are brainteasers here to stay? While opinions may differ, as seen in the comments to the LinkedIn posts, the fact is that firms like Goldman Sachs are using them. If you want to work at these firms, then you’ll have to deal with them, whether you agree with them or not.

If you’re gearing up for an interview where these types of questions might pop up, take the time to get familiar with the different types, practice your reasoning out loud, and remember to stay calm.

Forewarned is forearmed. With proper preparation, you can turn these challenging questions into opportunities to showcase your skills. 👍