The Ultimate CalcuDoku (Mathdoku) Puzzle Book: 500 Clever Ken Puzzles for Adults and Kids, Compact Logical Arithmetic Crossword Puzzles This 132-page CalcuDoku Puzzle Book features500 Puzzles6" x 9"white-colored papereasy, medium and hard calcudoku (mathdoku) puzzles4x4 and 6x6 size puzzlesWe've squeezed as many puzzes as possible into these 132 pages. In doing so, we've saved some trees and kept printing costs down (saving you a bunch). Eco-friendly, wallet-friendly and travel-friendly! You'll just love our clever (ken) puzzles. CalcuDoku Puzzle books are a great way to occupy yourself at home without the use of phones, tablets or laptops. This puzzle book has some hard puzzles for adults, as well as some easy puzzles for kids.