• Observations of students and partners throughout the lesson will serve to assess student progress.
• The Open Number Line Activity Sheet (M-1-2-2_Open Number Line Activity Sheet.docx) serves as a review of the strategies students were exposed to in Lesson 2 and can be used as a formative assessment.

Draw an open number line on the board. Show students how an open number line is helpful because you can use it for any numbers or ranges. Write a 32 on the number line; then count by ones and plot where 40 would be. Explain to students that the goal is to hop to the nearest 10. Continue this process until students seem to understand how the number line works.

Plot the number 35 on the number line. Ask students “How can I hop to 40 in just one hop?”

Ask for ideas. Draw the hop on the number line and label it with “+5” above the jump. Then record the number sentence 35 + 5 = 40. Plot the number 48 on the number line. Ask students “How can I hop to 50 in just one hop?” Have students share their ideas with a partner. Then choose one student to share out. Repeat this process with other off-decade numbers and ask students how to hop to the next decade.

Next plot the 35 on the number line again. This time ask students “How can you add 6 to 35 using two hops?” Have students talk with their partner about strategies for solving the problem.

Ask for volunteers. Students might say they would add 5 to get to 40, and then add 1 more.

Pose another problem, this time starting with the number 46. Ask students “How can you add 8 using two hops?” Repeat this process until students have a good understanding.

Then pass out an Open Number Line Activity Sheet (M-1-2-2_Open Number Line Activity Sheet.docx) to each pair. Allow students time to work together on the number-line hops.

Have the class come together in your meeting spot. Ask for volunteers to show the jumps they made for a few of the problems on their sheet.

Extension:

• Routine: The number of the date can be used to add to the next decade, or add across decades each day during a calendar routine.
  • 50 jump back 6
  • 60 jump back 4
  • 63 jump back 6 in two hops
  • 72 jump back 5 in two hops.

• Small Group: Have students practice adding single-digit numbers to decade numbers on the empty number line. Then you can start with single digits and add to get to 10.

• Expansion: Students who are easily making the jumps across the decades can begin working with subtracting from a decade number and subtracting across decades. For example: