Difficulty - Easy - Brain Easer

Difficulty - Easy, Riddles and Lateral Thinking

Mystery Killer Riddle

A detective is called upon to solve the riddle of the mystery killer in a high-profile murder.

There are only three suspects:

Aaron, the best friend
Patty, the gardener
Jason, the neighbor

The victim was holding a calendar, and it seems he marked several of dates before he passed away: the second of January, the sixth of February, the third of April, the fourth of October, and the first of November.

With this information, the detective identified the culprit. Who was it?

Difficulty - Easy, Logic Puzzles

Favorite Fruit and Favorite Color

Ava, Beth, Cam, and Derek each have a different favorite fruit and favorite color. We know their favorite fruits are apple, banana, cherry, and durian, and their favorite colors are blue, green, red, and yellow. We also know:

Cam does not like apples or cherries
Derek’s favorite color is yellow and his favorite fruit is not banana
The person whose favorite fruit is cherry also likes the color green
Beth’s favorite color is red and her favorite fruit is not apple
The person whose favorite fruit is durian does not like the color blue

What is each person’s favorite fruit and favorite color?

Difficulty - Easy, Matchstick Puzzles, Simple Math

Matchstick Equation 4

Move exactly 2 matches to make this a valid equation.

Bonus: find two different solutions.

In matchstick equation puzzles, you are not allowed to make an inequality symbol such as ≠, ≥, >, <, or ≤. That would make it too easy!

Chess, Difficulty - Easy

Mate in 2 Chess Puzzle 3

White to play and mate in 2.

Difficulty - Easy, Geometry

Maximize Triangle Area

If a triangle has two sides with lengths 3 and 4, what should the length of the third side be in order to maximize the area of the triangle?

Difficulty - Easy, Word Puzzles

Compound Word Puzzle 3

Compound words are words that are composed of two or more other words, like high + light = highlight.

Can you make compound words out of the following three words by adding the same 4-letter word either before or after each word?

CROSS
WORKS
WILD

Difficulty - Easy, Simple Math

Most Frequent Digit

What is the most frequent digit among the numbers between 1 and 1000 (inclusive)? Consider only base-10 whole numbers.

Difficulty - Easy, Interview Brain Teasers, Probability

Reroll the Die

Suppose there is a game in which you roll a fair, 6-sided die and win dollars equal to the outcome of the roll. How much would you expect to win on average?

Suppose, if you don’t like the outcome of the roll, you can reroll the die once, and win dollars equal to the outcome of the 2nd roll (once you choose to reroll, you can no longer go back to the 1st roll). How much would you expect to win on average?

Suppose, if you don’t like the outcome of the 2nd roll, you can reroll the die once more, and win dollars equal to the outcome of the 3rd roll (once you choose to reroll, you can no longer go back to previous rolls). How much would you expect to win on average?

This was an actual brain teaser question once asked at Jane Street for an interview for an intern role.

Difficulty - Easy, Matchstick Puzzles

Leave Two Squares

Remove 6 matches from the diagram above to leave two squares, with no extra matches lying around.

Difficulty - Easy, Riddles and Lateral Thinking, Simple Math

Password to Exclusive Club

A man wants to enter an exclusive club, but doesn’t know the password. He observes a few other patrons:

First patron walks up and the doorman just says “12”. The patron replies “6” and is let in.
Second patron walks up and the doorman says “6”. The patron replies “3” and is let in.

Thinking he has figured it out, the man walks up and the doorman says “10”. The man replies “5” but it’s incorrect and he is turned away.

What should the man have said instead?