**Grade 2 Module 2: Addition and Subtraction of Length Units**

In this Grade 2 module, students engage in activities designed to deepen their conceptual understanding of measurement and to relate addition and subtraction to length. Their work in Module 2 is exclusively with metric units in order to support place value concepts. Customary units will be introduced in Module 7.

**Topic A:**Topic A begins with students exploring concepts about the ruler. In Lesson 1, they relate length to physical units, by measuring various objects with multiple centimeter cubes. Students create a mental benchmark for the centimeter. In Lesson 2, they apply their knowledge of using centimeter cubes to measure by moving from repeated physical units to iteration of one physical unit. This enables them to internalize their understanding of a length unit as the amount of space between one end of the cube to the other (or space between hash marks). Thus, they begin moving from the concrete to the conceptual. Finally, in Lesson 3, they apply knowledge of known measurements to create unit rulers using one centimeter cube. This deepens the understanding of distance on a ruler and the ruler as a number line.

**Lesson 1: Connect measurement with physical units by using multiple copies of the same physical unit to measure.**

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__Instruction Guide:__**Lesson 2: Use iteration with one physical unit to measure.**

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__Instruction Guide:__**Lesson 3: Apply concepts to create unit rulers and measure lengths using unit rulers.**

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__I____nstruction Guide:__**Topic B:**Students begin using centimeter rulers, meter sticks, and meter tapes to measure various objects. Through the practice of measuring various items and learning mental benchmarks for measurement, students organically develop estimation skills in Lesson 5. They also develop their skills for selecting an appropriate measuring tool by referencing prior knowledge of objects they have already measured, as well as by using mental benchmarks.

**Lesson 4: Measure various objects using centimeter rulers and meter sticks.**

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**Lesson 5: Develop estimation strategies by applying prior knowledge of length and using mental benchmarks.**

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**Topic C:**In Topic C, students use different length units to measure and compare lengths. In Lesson 6, they practice applying their knowledge of centimeters and meters to choose an appropriate measurement tool. They discover that there is a relationship between unit size and measurement when they measure one object twice using different length units. They learn that the larger the unit, the fewer number of units in a given measurement. In Lesson 7, students continue to measure and compare lengths using standard and non-standard length units. At this point students are prepared to explicitly compare different nonstandard length units and can make inferences about the relative size of objects.

**Lesson 6: Measure and compare lengths using centimeters and meters.**

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**Lesson 7: Measure and compare lengths using standard metric length units and non-standard lengths units; relate measurement to unit size.**

**This is the link to see what the teachers use for classroom instruction.**__I____nstruction Guide:__**Topic D:**In Topic D, students relate addition and subtraction to length. They apply their conceptual understanding to choose appropriate tools and strategies (e.g., the ruler as a number line, benchmarks for estimation, tape diagrams for comparison) to solve word problems (2.MD.5, 2.MD.6). In Topic A, students had their first experience creating and using a ruler as a number line. Now, students solve addition and subtraction word problems using the ruler as a number line. This concept is reinforced and practiced throughout the module in the fluency activities that involve using the meter strip for counting on and counting back, and is incorporated into the accompanying Problem Sets. Students then progress in the second lesson from concrete to abstract by creating tape diagrams to represent and compare lengths. The third lesson culminates with students solving two-step word problems involving measurement using like units.

**Lesson 8: Solve addition and subtraction word problems using the ruler as a number line.**

**This is the link to see what the teachers use for classroom instruction.**__I____nstruction Guide:__**Lesson 9: Apply conceptual understanding of measurement by solving two-step word problems.**

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**Lesson 10: Concrete to abstract: measure lengths of string using measurement tools; represent length with tape diagrams to represent and compare the lengths.**

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