The sum of the numbers across is equal to the sum of the numbers down. 14 puzzles per set, plus answers. For use with Transparent Number Tiles. Your students will love solving these engaging puzzles while they sharpen their recall of basic facts, and improve their number sense and problem solving skills. Using tiles instead of pencil and paper allows children to explore different solutions just by moving tiles around, inviting all sorts of discoveries. The set offers a wide range of difficulty. The easiest will be accessible to most all students. The more difficult will challenge even the brightest. Puzzles are self-correcting and perfect for centers.