In Topic E, students transition to the more abstract number disks that will be used through Grade 5 when modeling very large and very small numbers. The foundation has been carefully laid for this moment since kindergarten when students first learned how much a number less than 10 needs to make ten. The students repeat the counting lessons of the bundles and money, but with place value disks (2.NBT.2). The three representations: bundles, money, and disks, each play an important role in the students’ deep internalization of the meaning of each unit on the place value chart (2.NBT.1). Like bills, disks are “traded,” “renamed,” or “changed for” a unit of greater value (2.NBT.2). Finally, students evaluate numbers in unit form with more than 9 ones or tens, for example, 3 hundreds 4 tens 15 ones and 2 hundreds 15 tens 5 ones. Topic E also culminates with a problem solving exploration in which students use counting strategies to solve problems involving pencils which happen to come in boxes of 10 (2.NBT.2).