This chapter contains fun and playful exercises to practise basic operations and arithmetics. Students can learn about number systems and in the Sequences topic there are more challenging tasks, involving proofs.

301 - Multiplication with Heights 302 - Secret Number 303 - Floor Plan Puzzle 304 - Secret Base 305 - Secret Exponent 306 - Binary System 307 - Number System with Base 4 308 - What Comes Next? 309 - Triangular Square Number 310 - How many Faces 311 - Growing Pine Trees