From Building a Wacky Hundreds Chart to Number Chart Bingo!, the twenty classroom-tested lessons and games in this resource transform the hundreds chart from a poster on the classroom wall into a hands-on, interactive tool used by both teachers and students. The hundreds chart is one of the most important tools teachers can manipulate to help students think about our base ten number system and to build a mental model of the mathematical structure of it. Working with the hundreds chart helps learners develop the skills they need to become flexible and fluent problem solvers, and meet the requirements of many state standards, including the Common Core State Standards.