Kakuro puzzle book for adults (Cross Sum & Product) 100 Easy puzzles (sum) - 100 Medium puzzles (sum) - 100 Hard puzzles (Product) - Solutions in the back - Pocket size (4.3×6) inch How to play Kakuro: Objective: Fill the blank cells with numbers from 1 to 9. Clues: Shaded cells indicate the sum of numbers in their row or column, or the product of the numbers in some puzzles. Rules: The numbers in each group (row or column) must equal the clue (either sum or product). - Numbers cannot repeat within a group. Strategy: Start with groups that have limited possibilities and use elimination.