CrossNumber Puzzle 2.1

Educational number puzzles for children. Level 2 covers addition and subtraction of nonnegative integers. Missing values appear on both sides of the equality to convey addition and subtraction as an abstract concept. For example, missing left hand term in addition is determined by subtracting from right hand result. That generalization prepares the child for the more advanced idea of an equation. The author, Jonas S Almeida is a Professor of Bioinformatics at the University of Texas and father of a 6 and 4 year old. These number puzzles were developed to help his children grasp basic concepts in Mathematics. This series is dedicated to his wife, Angela, who inspired the collection in a book format.