This four-book series is designed to promote thinking and reflection about numbers, leading students to develop a strong foundation in number sense. Students in primary through middle grades will explore patterns, develop mental-computation skills, understand different but equivalent representations, establish benchmarks, recognize reasonableness, and acquire estimation skills. Each book provides sections that explore the major components of number sense: Mental Computation Estimation Relative Size Multiple Representation Number Relationships Reasonableness The 10-minute activities can be used to supplement an existing curriculum whenever needed. They are designed to build on students’ thinking about numbers in meaningful ways so students develop the number sense needed to be successful in mathematics. The activities encourage dialog between students and teachers, and the quality of sharing is why this program is successful.