# 3.NBT.A.2

Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.

## Summary:

Students need a variety of strategies for solving addition and subtraction problems within 1000 including those that can be computed mentally. These strategies will provide students with a variety of choices when deciding the best way to solve problems. This skill contributes to a more thorough understanding of the relationships and properties between numbers.

## Understanding the Standard:

• Teachers should guide students through a wide variety of methods for solving addition and subtraction problems. While the correct answer is important, students need to feel comfortable in finding an answer in the way that makes the most sense to them while also having knowledge and practice with other strategies as well. Some strategies are more efficient than the standard algorithm in particular situations. For example, 41 - 2 is much faster if one simply counts down rather than regroup and subtract.
• Students should be required to communicate their reasoning for choosing a specific strategy. Additionally, they should be encouraged to justify their reasoning in a variety of manners (including the use of place value and properties of operations), and to support their explanations with (written or oral) words and with concrete objects, models, pictures, or drawings.
• Manipulatives and technologies are useful for all students and especially those who require more visual cues.

## Questions to Focus Instruction:

• Have students been exposed to a wide range of problem-solving tools that go beyond counting fingers and using a number line?
• Can students communicate their reasoning for choosing a specific strategy for problem-solving?
• Can students fluently add and subtract within 1000?
• Are students comfortable in using different strategies to solve addition and subtraction problems, including place value, properties of operations, and/or the relationship between addition and subtraction?
• Can students recognize that certain strategies are more efficient than the standard algorithm in particular situations?

## Skills

Prior to: Students can fluently add and subtract through 20 using mental strategies. Students have also been exposed to a multitude of strategies to add and subtract one and two-digit numbers through 100. Later, they will regroup ones and tens when necessary to solve an operations problem. Furthermore, students have already been exposed to addition and subtraction within 1000 in grade 2. Go to 2.NBT.B.52.NBT.B.7. to see previous skills in this progression.

At Grade Level: Students will fluently add and subtract within 1000 using a variety of strategies, knowledge of place value and properties of operations.