The best riddles. Anywhere.

Math Riddles

Math riddles require that you dig into arithmetic and calculation a little bit to figure out the solution. These riddles rarely involve advanced trigonometry or calculus, but adding and multiplying is fair game.

Easy

How can you place the numbers 1 through 9 in a 3x3 grid such that every row, column, and the two ...
Consider the following explanation for why 1=2 : 1. Start out    Let y = x 2. Multiply through by x ...
In a bouquet of flowers, all but two are roses, all but two are tulips, and all but two are ...

Medium

There are 1 million closed school lockers in a row, labeled 1 through 1,000,000. You first go ...
Using only and all the numbers 3, 3, 7, 7, along with the arithmetic operations +,-,*, and /, can ...
Andy, Barry, and Carl race each other in a 100-meter dash. They each run at a constant speed ...
Five coworkers want to know what the average of all their salaries is, but refuse to reveal ANY ...
The King of a small country invites 1000 senators to his annual party. As gifts, each senator ...

Hard

Consider a 10-character string consisting of the numbers 0 through 9, with each number appearing ...