Whether it's multiplying two three-digit numbers, multiplying by a specific large number like 76,923 or 5,882,353, dividing by anything up to 50 accurate to a large number of decimal places, or figuring out the number of days between dates or what day of the week a date was, this book will teach you how to do that in your head. Do you use the Standard Method by multiplying each digit one at a time? Do you use the Stretch Out Method by adding something to one number and subtracting something from the other number? Do you use the Almost-Round Multiple Method by finding a multiple of one of the numbers that's easy to multiply by? You choose which method is easiest for you. This book is mainly for those who already understand the basic concepts of math and wish to be able to do math in their head. It is not a substitute for tutoring for those who struggle with math.