Largest and smallest numbers

Harry O’Brien is an experienced primary-school teacher and an award-winning author. Through working in a wide range of schools with various socio-economic backgrounds, Harry has developed a finely tuned understanding of what students can achieve and draws on this knowledge in his writing. Over a period of 25 years he has written numerous bestselling primary textbook series, including the Maths Plus Series. Harry is the creator and major author of the highly successful Maths Box: Lime, Orange and Aqua and the Reading Box: Yellow, Blue, Red and Green. In addition to his busy publishing and writing workload, Harry oversees the day-to-day running of Teachers 4 Teachers Publications Pty Ltd.