Draw some circles, the vertices, connected by lines, the edges. Make sure there are no loops in the structure. These are your “trees” or “insectoids” for the puzzle. Next: Fill the circles in with consecutive odd numbers, then write their differences on the connecting lines. Numbers should not repeat. This is the Graceful Tree Conjecture or the Ringel-Kotzig conjecture.
He also discusses the most challenging versions of the Graceful Tree Conjecture. Hamilton uses this math puzzle in elementary school classes to help strengthen students’ subtraction and problem-solving skills.
Next: Anastasia Chavez explains the 21-card trick, Universal Calendar Puzzle: Figure out the day of the week for any date ever, how to multiply numbers by drawing lines, and can you solve the penniless pilgrim riddle?
We also recommend these math activity books: Bedtime Math and One Minute Mysteries: 65 Short Mysteries You Solve with Math!