This is volume 1 in a series of books of 7 x 7 CrossFigure puzzles.A CrossFigure is like a crossword, but it uses numbers instead of letters.Each digit occupies a square and can be part of a "word" in the across and down directions.Each clue is a mathematical relationship with other clues. For example, a puzzle might have the clue that 1 Across equals 4 Down plus 6 Across.Visit http: //3DMathPuzzles.com to download free CrossFigure, TripleCross, and 3D puzzles!