How to Calculate Quickly: Full Course in Speed ArithmeticMany useful procedures explained and taught: two-column addition, left-to-right subtraction, direct multiplication by numbers greater than 12, mental division of large numbers, more. Also numerous helpful short cuts. More than 8,000 problems, with solutions. This book do not used trick but teach you "number sense" ... and how to calculate from left to right with complex number. Believe me, I was afraid of that kind of calculation and with that book I learned a lot!