Boy or Girl Paradox

The “boy or girl paradox” is a well-known brain teaser by famous puzzle-maker Martin Gardner. It’s popularly considered a “paradox” because (1) it has a highly unintuitive solution, and (2) its ambiguous wording meant either of two solutions could be…

Two Envelopes Paradox

The two envelopes paradox is a famous brain teaser of sorts, and not a true paradox. The problem is generally posed like this: You are given a choice between two identical envelopes. One envelope contains some amount of money, and…

Friedman Numbers

Friedman numbers are positive integers that can be written as an expression of its own digits and basic arithmetic operations. While Friedman numbers don’t have much practical use, they can be fun and creative puzzles for all ages! Rules of…

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: The victim was holding a calendar, and it seems he marked several of dates before he passed away:…

5 Quant Brain Teasers

Whether you’re preparing for an interview or just trying to keep your mind sharp, here are some quant brain teasers to test your skills. Remember, if you get a brain teaser at an interview, you don’t necessarily need to get…

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…