This is a terrific logic exercise. Logic is a basis for advanced thinking: "If this is true, then, that is true."
Parade Magazine contributor, Marilyn vos Savant, created a logic puzzle where an individual, when given a set of numbers within a grid, has to analyze and determine the remaining numbers 1-81. The numbers may only move numerically by row or column, not diagonally. When successfully completed, a line drawn from 1-81 will not intersect. The puzzles are listed by level of difficulty. They may be played online or printed.
The puzzles have varying degree of difficulty.