File under factors, multiples, square numbers, prime numbers, and sequences: This classic mystery novel set up has a wonderful math puzzle twist:

Your rich, eccentric uncle just passed away, and you and your 99 nasty relatives have been invited to the reading of his will. He wanted to leave all of his money to you, but he knew that if he did, your relatives would pester you forever. Can you solve the riddle he left for you and get the inheritance? Lisa Winer shows how.

Don’t forget to hit pause and try to work out the problem before the solution is revealed! Then watch it again as mathematician James Grime flips Othello pieces over in Maths Puzzle: Back to Black:

In the archives: More puzzles and numbers, including the mathematical secrets of Pascal’s triangle, Mathematica – A World of Numbers… and Beyond, and One is one…or is it?