Math Mammoth Subtraction 1 is a worktext that is most suitable for first grade math. It contains full instruction, written to the student, and a variety of exercises and problems, all in one book. The first part of the book covers the concept of subtraction, the relationship between addition and subtraction, and the various meanings of subtraction. The latter part focuses on memorizing the basic addition and subtraction facts and on word problems. The first lesson, Basic Subtraction, reviews the basic meaning of subtraction as “taking away.” The student writes subtraction equations from illustrations, and solves problems by drawing dots and crossing out some of them. The next lessons have to do with subtracting on the number line and counting down to subtract. Counting down is a transitional strategy for subtraction, because later students will learn more efficient ways, but it is important conceptually. The following lesson, Subtraction and Addition in the Same Picture, begins the study of the relationship between addition and subtraction. This concept will span several lessons. This first lesson presents two sets of objects, such as blue and white balls, and the student writes both an addition sentence and a subtraction sentence from this illustration. In the lesson Two Parts—One Total, we study word problems that do not involve the idea of taking away but have two parts making up a total. For example, if there are 10 flowers of which some are white and some are red, and seven of them are white, how many are red? Then we study fact families. This means writing two additions and two subtractions using the same three numbers. In the three lessons covering How Many More?, students find how many more or how many fewer objects one person has than the other by drawing the objects. In the next lesson, Differences, we continue the theme, this time writing a missing addend addition for problems that ask “how many more” using a number line to help us see the difference between numbers. The second part provides lots of practice for learning and memorizing the basic addition and subtraction facts with numbers from 0 to 10. The lessons approach the fact memorization from the concept of fact families, which makes the process logical and structured. Besides the written problems, I encourage you to use the games listed in the introduction of the book. The answer key is appended. This is the 2026 edition.