# Introduction
Wall Street interviewers love brainteasers.
They throw counter-intuitive probability puzzles at you.
The kind you never saw in math class.
## Misconception 1: “We don’t care about the answer”
Interviewers often say, *“We only care how you think, not if you solve it.”*
Sounds nice. Not true.
Imagine the candidate before you. He memorized 100 brainteasers. He nails five in a row.
Then it’s your turn. You think out loud beautifully. But you don’t get to the answer.
Who gets the job? Exactly.
So yes—getting the right answer matters.
## Misconception 2: “You don’t need to prep”
Another myth: *“These test raw problem-solving. No prep needed. Just brush up probability theory.”*
Wrong.
Yes, they want problem-solvers. But here’s the reality:
Reading probability theory is like looking at a picture of a hammer, then being asked to build a table.
You could, given enough time, figure these puzzles out yourself.
But in an interview? Under pressure? With a stopwatch? Very few do.
Unless you’ve seen similar problems, most don't even know where to start.
## Solution 1: Make the interviewer your ally
This part is overlooked. It’s huge.
When the interview begins, they’ll ask about your resume, your background, the role.
Most candidates just recite their resume and give with pre-memorised answers.
Don’t. You'll miss a golden chance to make a friend.
Ask about them. Be curious. Smile. Make it human.
“Ah, so you also worked on XYZ? What’s the best part of that job? How did you decide to go for that job?”
A little joke helps: when they say, *“Okay, let’s move to technical questions,”* you smile: *“Let’s go—just have mercy.”*
The point is: turn a cold transaction into a friendly exchange.
Why does this matter?
Because people help people they like.
Once you’ve built that connection, interviewers will *want* to guide you.
They’ll drop hints. They’ll nudge you.
It’s the same reason you tip the waiter who asked about your day, even if the food was nothing special.
And if you light up when you get a hint—*“Ah, interesting, I didn’t think of that!”*—you look like someone who loves solving problems.
The result: you relax, they relax, and suddenly the problem feels easier.
Being pleasant does half the job.
And since many interviewers aren’t social butterflies, you’ll stand out immediately.
## Solution 2: Learn the toolbox
The other half of the job is knowing the tricks.
Every brainteaser hides a shift in perspective.
There aren’t infinite tricks. A few show up again and again, in different costumes.
Your job is to recognize which tool to use—hammer, wrench, screwdriver.
That’s what I'm going to do for you.
Seven days. The most common tricks. The mental toolbox you can grab from under pressure.
Once you’ve seen them, you’ll know where to start.
Often that’s all it takes.
**Disclaimer**
As you go through the course, don't panic if you can't spot the pattern between different questions. It's by design.
We'll take you through as diverse a set of brainteasers as possible. So you see each trick at least once.
If you have 7 days to prepare, just follow this course - it's your best shot.
If you have more time, go through the course, download the cheatsheet and go practice questions in the brainteasers page. Each of them has a 'hint' that tells you which trick to use.
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Let’s begin.
You’ve got this.