standard_description: Interpret multiplication as scaling (resizing), by:
- Explaining why multiplying a given number by a fraction greater than 1 results in a product greater than the given number (recognizing multiplication by whole numbers greater than 1 as a familiar case); explaining why multiplying a given number by a fraction less than 1 results in a product smaller than the given number; and relating the principle of fraction equivalence a/b = (n×a)/(n×b) to the effect of multiplying a/b by 1.
- Comparing the size of a product to the size of one factor on the basis of the size of the other factor, without performing the indicated multiplication.
problem_activity: Narrative
In this activity, students reason about the relative size of decimals by locating them on a number line. As in a previous activity, they rely on their experience of locating fractions on a number line and the relationship of the decimal values relative to 0 and 1.
If desired and logistically feasible, consider carrying out the activity on a giant number line rather than on paper.
Stretch a long strip of tape across a wall, at least 8 or 10 feet long. Partition the tape into 12 equal intervals, using shorter pieces of tape as tick marks. Label the locations of 0 and 1.
Give each group of students 2–3 dot stickers, 4–5 sticky notes, and a thick marker.
Ask each group to write (on sticky notes) labels for two of the tick marks, with one sticky note for each label.
Assign each group one or two of the eight decimals in the second problem. Ask them to locate their assigned decimals on the number line, using dot stickers to mark the location and sticky notes to label them.
Action and Expression: Internalize Executive Functions.
Synthesis: Invite students to plan a strategy, including the tools they will use, for the first two steps of the activity. If time allows, invite students to share their plan with a partner before they begin.
Supports accessibility for: Organization, Social-Emotional Functioning
Launch
Groups of 3–4
Activity
If creating a giant number line, lead the activity as outlined in the Activity Narrative. Otherwise, ask students to work with their group on the first two problems.
Pause and discuss:
how students knew where to put each decimal
how the number line could help us see the least and greatest
“Take a few quiet minutes to complete the rest of the activity.”
5–6 minutes: independent work time
Student Facing
Label each tick mark on the number line with the number it represents.
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Here are eight numbers.
0.10
0.40
0.80
1.10
0.15
0.45
0.75
1.05
Locate and label each number on the number line.
Which number is greatest? Which is least? Explain how the number line can help determine the greatest and least numbers.
Locate and label these numbers on the number line.
0.24
0.96
0.61
1.12
0.08
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Use two numbers from the previous questions to complete each comparison statement so that it is true.
________ is greater than _______.
________ is less than _______.
________ is the greatest number.
Student Response
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Advancing Student Thinking
Students may be unsure whether to label the tick marks between 0 and 1 in terms of tenths or hundredths, or whether to use fraction or decimal notation. Consider asking: “What labels might be helpful for locating the decimals in the activity?”
Activity Synthesis
Select students to display their completed number lines (showing the locations of five additional decimals).
Invite the class to agree or disagree with the locations of the point and discuss any disagreements.
Select other students to share their comparison statements and how they know each statement is true.


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