As a result of media and parental attention to need for improvement of core skills, this is a fast-paced mental arithmetic book to encourage mastery of two of the four rules of number. Following on from the starter complete mastery books this book brings together the number skills mastered and adds extra mathematical ideas. The book recommends that children spend 15 minutes each day using this book to compete against themselves or against friends. They do the tests again and again becoming increasingly accurate and beating their own times. Eventually they should be able to do all the sum in 30-seconds and become a "30 second champion"! Children need scrap paper, a watch with a second hand, scrap paper and a calculator.