Lesson 14
Nearest Multiples of 10 and 100
Warmup: Estimation Exploration: What Number Could this Be? (10 minutes)
Narrative
The purpose of this Estimation Exploration is for students to think about what value a point on the number line could represent. The only labeled tick marks are hundreds so students need to reason about what numbers are in between and how far the point is from the labeled numbers.
Launch
 Groups of 2
 Display the image.
 “What is an estimate that’s too high? Too low? About right?”
 1 minute: quiet think time
Activity
 “Discuss your thinking with your partner.”
 1 minute: partner discussion
 Record responses.
Student Facing
What number could the point on the number line represent?
Record an estimate that is:
too low  about right  too high 

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Student Response
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Activity Synthesis
 Consider asking:
 “Is anyone’s estimate less than _____? Is anyone’s estimate greater than _____?”
 “Based on this discussion does anyone want to revise their estimate?”
 “What would help us be more sure of our estimate?” (More tick marks that are equally spaced. Marks of multiples of 10.)
Activity 1: Close to Multiples of 10 (20 minutes)
Narrative
Previously, students identified two multiples of 100 that border a given number, reasoned about their relative distance from the number, and then named the nearest multiple of 100. The purpose of this activity is for students to practice naming the nearest multiple of 100 and apply the same reasoning to identify the nearest multiple of 10. They determine two multiples of 10 that are closest to a given number (two intermediate tick marks on the number line) and then identify the multiple of 10 that is closer.
Engagement: Provide Access by Recruiting Interest. Leverage choice around perceived challenge. Invite students to select at least 3 of the 5 problems to complete.
Supports accessibility for: Organization, Attention, Socialemotional skills
Launch
 Groups of 2
 “Locate and label each number in the table on the number line. Then, find the nearest multiple of 100. Leave the last column blank for now.”
 3–5 minutes: partner work time
 Share responses.
Activity
 “Now, complete the second problem with your partner. Be prepared to share your reasoning.”
 1–2 minutes: partner work time
 “How did you decide which multiples of 10 were closest to 128?” (Sample responses: I looked at which multiples of 10 it was in between. I looked for a multiple of ten to the right and a multiple of 10 to the left, these were the closest.)
 Have students label the last column and record the multiple of 10 that was closest to 128.
 “Complete the last problem independently.”
 3–5 minutes: independent work time
Student Facing


Locate and label each number on a number line.
128
272
436
89
351

The same numbers are listed in the table. Name the multiple of 100 that is the nearest to each number. (Leave the last column blank for now.)
number nearest multiple of 100 128 272 436 89 351


Look at the point for 128 on the number line.
 Name two multiples of 10 that are the closest to 128.
 Which of the two is the nearest multiple of 10?
 Label the last column in the table “nearest multiple of 10.” Then, name the nearest multiple of 10 for each number. Use the number lines if you find them helpful.
Student Response
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Activity Synthesis
 “How do you know which multiple of 10 is the nearest for each number?” (If we label and locate the number on the number line, we can see which tick mark the point is closer to. We can see how many numbers to count up or down to get to a multiple of 10. For example, we only count up once to get from 89 to 90, but we count down 9 times to get down to 80.)
Activity 2: The Nearest Multiples (15 minutes)
Narrative
In this activity, students identify the nearest multiples of 10 and 100 for given threedigit numbers. 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 and decide not to use number lines. The work here prepares students to reason numerically in the next lesson.
When students notice and describe patterns in the relationship between the numbers and the nearest multiples of 10 or 100, they look for and express regularity in repeated reasoning (MP8).
Advances: Conversing, Reading
Launch
 Groups of 2
 “Let's find more multiples of 10 and 100 that are close to some numbers.”
 “Notice that no number lines are given. See if you can still find the nearest multiples of 10 and 100 without them. If you need to, you can still use a number line.”
Activity
 “Work with your partner to complete these problems.”
 5–7 minutes: partner work time
 Monitor for students who use the following strategies to highlight:
 Reason about the midpoint between a multiple of 10 or a multiple of 100 (5 or 50) to determine which multiple is closer, such as, “568 is closer to 570 because 565 would be the middle point between 560 and 570.”
 Use place value patterns to determine which multiple is closer, such as, “Since the 1 in 712 is less than 5, it tells me that the number is closest to 700.”
 Pause for a brief discussion before students complete the last problem.
 Select previously identified students share the strategies they used to find the nearest multiple of 100 and the nearest multiple of 10.
 “Now take a few minutes to complete the last problem.”
 2–3 minutes: independent work time
Student Facing


Is 349 closer to 300 or 400?

Is 349 closer to 340 or 350?



Is 712 closer to 700 or 800?

Is 712 closer to 710 or 720?



Is 568 closer to 500 or 600?

Is 568 closer to 560 or 570?


Without locating a given number on a number line, how did you decide:
 the nearest multiple of 100?
 the nearest multiple of 10?

Name the nearest multiple of 100 and the nearest multiple of 10 for:
 324
 89
Student Response
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Advancing Student Thinking
If students don’t identify the closest multiple of 10 or 100, consider asking:
 “What have you tried to find the closest multiple of 10 (or 100)?”
 “How could you use a number line to find the closest multiple of 10 (or 100)?”
Activity Synthesis
 Invite students to share their responses and reasoning for the last problem.
Lesson Synthesis
Lesson Synthesis
“Today we found the nearest multiple of 100 and the nearest multiple of 10 to a given number. When we name another number that is close to a given number, we are rounding the given number. For example, we can round 568 to 570 or to 600. Often, the numbers we use for rounding are multiples of 10 or 100.”
“If we want to use round to say ‘find the nearest multiple of 10,’ we can say ‘round to the nearest ten.’ We can use round with hundreds too. Instead of saying ‘find the nearest multiple of 100,’ we can say, ‘round to the nearest hundred.’”
Cooldown: Closest Multiple of 10 and 100 (5 minutes)
CoolDown
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