standard_description: Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
problem_activity: Narrative
In this activity, students identify the nearest multiples of 10,000 and 100,000 for the six-digit numbers they saw in the first activity. They may do so by using the number lines from earlier, but they may also start to notice a pattern in the relationship between the numbers and the nearest multiples without the number lines (MP7).
MLR8 Discussion Supports.
Display sentence frames to support small-group discussion: “I noticed _____ so I . . .” and “I agree/disagree because . . . .”
Advances: Conversing, Representing
Launch
Groups of 2 or 4
Display number line with endpoints of 100,000 and 200,000.
Activity
“Take a few quiet minutes to work on the activity. Then, share your responses with your group.”
6–7 minutes: independent work time
3–4 minutes: group discussion
Student Facing
Use the number line that represents the numbers between 100,000 and 200,000 for this activity.
Name the multiple of 10,000 that is the nearest to each number. (Leave the last column blank for now.)
| number  | nearest multiple of 10,000 | \(\phantom{nearest multiple}\) |
|---------|----------------------------|--------------------------------|
| 100,025 |                            |                                |
| 128,201 |                            |                                |
| 140,261 |                            |                                |
| 158,002 |                            |                                |
| 194,030 |                            |                                |
Here is the number line with 215,300 shown on it. Which multiple of 100,000 is the nearest to 215,300?
[IMG]
Label the last column in the table “nearest multiple of 100,000.” Then, name the nearest multiple of 100,000 for each number in the table.
Student Response
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Advancing Student Thinking
Students may see that the nearest multiples of 10,000 for a number are the two tick marks surrounding the point but may be unsure what numbers they represent. Ask them to recall what each tick mark represents on this set of number lines and urge them to count the marks.
Activity Synthesis
Display the blank table from the activity. Invite students to share their responses to complete the table. Discuss any disagreements.
Invite students to share how they identified the nearest multiples of 10,000 and 100,000.
If no students mentioned that they examined the location of each point visually and decided the closest tick marks on the number line, ask them about it.


aligns: no