Brain Teasers and Puzzles

Brain teasers, puzzles, riddles, and other challenges

Difficulty - Easy, Physics and Science

Throwing a Ball

When you throw a ball straight up, does it spend more time going up, more time coming down, or the same time going up and down – taking into account both gravity and air resistance?

Difficulty - Medium, Interview Brain Teasers, Probability

You are driving to Seattle to meet some friends, and want to know whether you should bring an umbrella. You call up 3 of your friends who live there and independently ask them if it’s raining. Your friends like to mess with you, so each of them has a 1/3 chance of lying. If all 3 friends tell you it is raining, what is the probability it is actually raining there?

This question was asked in an actual Facebook data scientist/data analytics interview.

Preparing for a brain teaser interview? Check out our ultimate guide to brain teaser interviews.

Difficulty - Very Easy, Number Theory

Seven Times the Sum of Its Digits

Which two-digit numbers are exactly equal to seven times the sum of its digits?

Difficulty - Hard, Patterns, Sequences, and Sets

Sequence Puzzle

Find the next two terms in this sequence:

10, 11, 12, 13, 14, 15, 16, 17, 21, 23, 30, 33, ?, ?

Chess, Difficulty - Very Easy

Mate in 12

White to play and mate in 12. Sometimes thinking 12 moves ahead in chess is not as hard as it seems!

Difficulty - Very Easy, Word Puzzles

Slowing and Shrinking

Remove one letter from the word “SLOWING” to make another valid English word. Repeat this step until you are left with just one letter, ensuring every step results in an English word. What words did you make in the process?

Difficulty - Easy, Interview Brain Teasers, Probability

Game the Coin Flip Game

A small company is losing money and the boss is looking for ways to cut costs. The boss is a foolish gambler, so he offers two employees the choice of either taking flat 10% pay cut, or playing the following coin flip game for each paycheck:

The employees each flip a fair coin – 50% heads and 50% tails; the boss will ensure they are not pulling any tricks.
They can see their own outcome but not the outcome of the other employee’s coin flip. They must then guess the outcome of the other employee’s coin flip.
If at least one of them guesses correctly, they get their full paycheck.
If both of them guess incorrectly, they get nothing.

The two employees take some time to work out a strategy, and then confidently accept the offer to play the coin flip game.

What strategy did they come up with that made them confident the coin flip game will give them more money?

Cryptography and Codes, Difficulty - Hard, Interview Brain Teasers, Word Puzzles

Secret Translation

The CIA intercepted some messages from a criminal organization, some in English and some in an unknown foreign language or code. As a CIA analyst and translator, you have figured out the following sentences and their English translations, but you do not yet know which sentence matches which translation:

Casara ashter osar
Intara amar
Intara orter osar
Alatara inter osar
Ortara amar
Alatara orter osar

I see a spy
I run
You see me
You see a spy
A suspicious man sees an enemy
You run

You have the opportunity to send a message in order to provoke a reaction from the criminal organization. Can you figure out and match up the translations above, and then send a message saying “a suspicious man runs” in this foreign language?