Can you insert all 10 pennies into the square opening of the puzzle? It looks easy, but maybe not... Enjoy great fun with this brain teaser that may take you 2 minutes or 2 days. Features: Recreational Mathematics: Circle packing puzzles are a fascinating branch of recreational mathematics, where the goal is to pack unit circles into the smallest possible square. Unique Challenge: The 10 circle problem offers the perfect level of difficulty, with a solution that is not at all obvious. Precision Cut: The opening is precision cut so the pennies just fit in with no room to spare, adding to the challenge. High-Quality Construction: Text is deeply laser engraved, and the backing is made from heavy-duty floorboard for a great weight and feel. Unsolved Puzzle: Comes unsolved with a temporary home for the tenth penny, which you must find a way to insert into the large opening. Solution Provided: The solution is included for when you need a hint or want to check your work. Handmade in the USA: Crafted in our Hudson, Florida shop, ensuring quality and attention to detail. Great Desktop Puzzle: Perfect for your desk, this puzzle is not only a fun challenge but also a fantastic conversation starter. Dimensions: 3.75" x 4" x 0.3"