Teaching Video Watch my colleagues' and my instructional video on how to teach three digit addition with regrouping through the use of base ten blocks and a place value mat. This activity aligns with the grade 2 math Common Core State Standard of "using placing place value and properties of operations to add and subtract." By using manipulatives, such as base ten blocks, students are able to form a better conceptual understanding of abstract ideas, like addition. Standard: CCSS.MATH.CONTENT.2.NBT.B.7 Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.