Unlock the world of math in the most exciting way possible with "Math Riddles " This interactive full-color puzzle book is designed to spark the imagination of children ages 6-12 helping them develo……続きを見る
This book is a collection of simple and easily grasped tricks to speed up your mental arithmetic. If you want to master them you should realize that to be used fully they need to be approached consc……続きを見る
