As a warm-up, try to solve the Lo Shu, the 3×3 magic square using numbers 1-9. Each of the 8 lines adds up to 15. Puzzle D is an example of a graceful graph. A harder problem is the Kelvin conjecture: if the soap bubbles in a froth each contained equal amounts of air, what would they look like? Turns out the bubbles would look like Weaire-Phelan foam. At the Beijing olympics, the Water Cube is actually a large scale mathematical sculpture based on Weaire-Phelan foam. Other 8-related magic: the 24-cell has 6(2^19 · 5688888889 + 347) distinct nets, 3778888999 has multiplicative persistence 10, and the squares of 6666667, 665949276513522, and 9949370777987917 are all interesting.