An original Mathematics book with various creative exercises, enriched with puzzles and brain teasers and all kinds of mental games. It is structured in 20 Exercise Units, of varying difficulty, and is accompanied by a brief theory, as well as detailed solutions with various methods-strategies that help in their better understanding. It discreetly follows the material of the school book of the 4th grade of Primary School for Mathematics and functions repetitively and creatively at any given time.