Children in prekindergarten focus on counting and gradually master the essential one-to-one matching of an object to a number. By the end of second grade, they can represent one, two and three digit numbers, understand simple fractions and apply a variety of facts and strategies to add and subtract skillfully. Investigations in this book support this progression by inviting students to count and order ducklings in a line, compute the total cost of several items on a menu and play a variety of games that reinforce their understanding of number, addition and subtraction. Problems in story form develop students' listening skills and immerse them in real-world mathematics. The supplemental CD-ROM features interactive electronic activities, master copies of activity pages for students and additional readings for teachers.