Cube (algebra) however, easy to show that most numbers are not perfect cubes because "all" perfect cubes must have digital root 1, 8 or 9. That is their values modulo 9 may be only −1, 1 and 0. Moreover, the digital root of any number's cube can be determined by the remainder the number gives when divided by 3: Every positive integer can be written as the sum of nine (or fewer) positive cubes. This upper limit of nine cubes cannot be reduced because, for example, 23 cannot be written as the sum of fewer than nine positive cubes: The equation has
Dino Cube Dino Cube The Dino Cube is a cubic twisty puzzle in the style of the Rubik's Cube. It was invented in 1985 by Robert Webb, however it was not mass-produced until ten years later. It has a total of 12 external movable pieces to rearrange, compared to 20 movable pieces on the Rubik's Cube. Robert Webb designed and made the first prototype of what would become the Dino Cube in 1985; his original prototype was made entirely out of paper. Since then the puzzle was reinvented twice, but full mass production of the puzzle did not start until 1995. The