Students developed strategies to add multi-digit numbers within 100 in first grade. While the strategies students likely used are not necessarily generalizable to any numbers within 100, they are sensible and relatively efficient [e.g., 28 + 35 = (28 + 2) + (35 -2) = 30 +33 = 63]. Further, these strategies are likely to be representative of those used when older students and adults solve multi-digit addition problems mentally. In second grade students began exploring multi-digit subtraction. There is focused time throughout second grade spent on helping students make sense of strategies to add and subtract multi-digit numbers. By the end of second grade the CCSS-M states that students should develop fluency using algorithms that are grounded in their understanding of place value for adding and subtracting multi-digit numbers within 100 and they should have strategies for adding and subtracting within 1000. While students are likely to vary in their competency with and understanding of addition and subtraction algorithms upon entering third grade, the focus of this unit is to help students deepen their understanding of place value and use this understanding to support fluency adding and subtracting within 1000.In this unit, students read, write, compare, and order numbers up to one hundred thousand (extending to one million in fourth grade). As part of this work they write equivalent numbers using standard and expanded notation. They use words, symbols, and some combination of the two to write, build, and speak numbers (e.g., 5327 = 5 thousands + 3 hundreds + 2 tens + 7 ones). Incorporating place value understanding is critical in this unit as this structure serves to help students learn to use procedures (i.e., algorithms) with connections to mathematical meaning. These connections support the development of number sense so that students are less likely to make computational errors, realize when their answers do not make sense, and solve problems efficiently and accurately. Place value continues to be important as students use estimation (e.g., rounding numbers to the nearest 10 or 100) in this unit to solve addition and subtraction problems. Students reason about the results they obtain from estimation and consider whether the solution that uses estimation is precise enough for the task at hand. Students also use estimation to judge the reasonableness of their and their peers' answers.This unit provides an important bridge to fourth grade, the year which students are expected to have developed fluency adding and subtracting multi-digit numbers using algorithms. Students in fourth grade are also expected to secure their understanding of place value up to 1,000,000. While this unit establishes connections between place value and addition and subtraction algorithms, it also provides a bridge to the multiplication and division work that students do in later units in third grade. Such connections will be extended in fourth grade as students learn to solve more complex multi-digit multiplication and division problems.As you teach this unit, and others focusing on the development of algorithms, please keep the following quotes in the forefront of your instructional decisions:

- Subject:
- Mathematics
- Material Type:
- Unit of Study
- Provider:
- OS/MAISA
- Date Added:
- 03/22/2018