Make math matter to students in grades 1Ð3 using Fact Mastery: Addition and Subtraction! This 176-page book helps students master fundamental facts now to prepare them for advanced math later. Students recall basic addition and subtraction facts by using strategies that build understanding of numbers. The book includes more than 75 half-page drills on sums and minuends up to 20, 15 mega-fun games, and 40 timed tests. The book supports NCTM standards.