Topic A begins with students solving word problems with three addends (1.OA.2) as a way for them to begin to explore the make ten Level 3 strategy in a meaningful context. With problems that always include at least two numbers that yield 10 when added together, Lesson 1 encourages students to use the associative and commutative properties as they set up and read equations in various ways. The story problem on the right, for instance, can be solved by adding 1 + 9 first, then adding the five (see image below story problem). This leads into Lesson 2’s focus of explicitly using the associative and commutative properties to add three addends without the context of story problems (1.OA.3). This lesson is where students practice associating the two addends that make ten (1.OA.6), and then adding the third addend; they prove to themselves that this simplification of addition is a viable strategy. Following this introduction, Lessons 3, 4, and 5 afford students ample practice with adding 9 and another single-digit number as they decompose the second addend to make ten with the 9. Students solve problems such as, “Maria has 9 snowballs and Tony has 6. How many do they have in all?” as follows: 9 + 6 = 9 + (1 + 5) = (9 + 1) + 5 = 10 + 5 = 15. This triad of lessons takes students through a concrete–pictorial–abstract progression as they work with physical 5-groups using objects, 5-group drawings, and finally number bonds. Lesson 6 reminds students of the commutative property again, by focusing them on when and why they might apply commutativity: to compose ten from the larger addend. Lessons 7, 8, and 9 mirror the earlier set of three lessons, but students decompose one addend to make ten with 8 as they key addend. This extensive practice allows students to internalize both why and how they would compose ten from the larger addend as they come to realize that this is an efficient strategy. Students use the make ten strategy with 5-group drawings and number bonds to solve a variety of problems involving a mixture of 7, 8, or 9 as addends in Lesson 10. This gives students an opportunity to not only practice their newly discovered strategies, but it also allows them to generalize this make ten strategy to a new number: 7. It is important to note that students can continue to use counting on as a strategy throughout this entire Topic A, although many students will begin to use the make ten strategy more and more as they continually discuss addition strategies and efficiency with one another. Topic A ends with Lesson 11, where students solve story problems with two addends (1.OA.1), using independently selected methods. With students themselves asking each other, “Why did you solve the problem that way? How did we solve these differently?” students are able to engage in rich dialogue about the mathematical strategies and determining which are most useful.

## Grade 1 Mathematics Module 2, Topic A

## Downloadable Resources

## Common Core Learning Standards

CCLS | State Standard |
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1.OA.1 | Use addition and subtraction within 20 to solve word problems involving situations of adding to,... |

1.OA.2 | Solve word problems that call for addition of three whole numbers whose sum is less than or equal... |

1.OA.3 | Apply properties of operations as strategies to add and subtract.3 Examples: If 8 + 3 = 11 is known... |