options: Number Systems and Quantity: students learn to understand the complex number system and reason quantitatively.

Modeling: students learn to choose and use appropriate mathematics and statistics to analyze real-world empirical situations, improve decisions, and report on their conclusions and the reasoning behind them.

Number & Operations in Base Ten: students learn to work with the base-ten system and build place value understanding.

Measurement & Data: students learn to work with data and measure attributes such as time, money, length, area, and volume. They may learn to compare measurements to operations and convert between different units of measure.

Statistics & Probability: students learn to analyze and produce data distributions, and build understanding of univariate and bivariate data. They learn to interpret data, make statistical inferences, justify conclusions, understand rules of probability, and use probability to make decisions.

Number & Operations - Fractions: students learn to understand fractions as numbers and may work with them using addition, subtraction, multiplication, and division.

Counting & Cardinality: students learn to know number names and the count sequence, count to tell the number of objects, and compare numbers.

Geometry: students learn to classify geometric figures by their properties, and understand and compare the relationships between them. Students develop and use formulas to compute lengths, areas, and volumes, and they use transformations to generate new shapes and compare existing ones. Geometry can be studied with and without coordinates.

Ratios & Proportional Relationships: students learn to recognize, describe, represent, and reason with ratios, rates, proportional relationships, and percent.

Operations & Algebra: students learn to solve problems using algebraic thinking and operations such as addition, subtraction, multiplication, and division. They may learn to identify and explain arithmetic patterns, evaluate or manipulate numerical expressions, and reason with equations and inequalities.

Functions: students learn to define, use, and evaluate functions to model relationships between quantities.
problem_activity: Narrative
The purpose of this activity is for students to begin to distinguish rectangles from other shapes. By working with variants and non-examples of rectangles, students begin to develop their understanding of what makes a shape a rectangle. When they discuss which group a shape should be placed in, students informally describe the attributes of the shape.
MLR8 Discussion Supports.
Students should take turns finding a match and explaining their reasoning to their partner. Display the following sentence frames for all to see: “I noticed _____, so I matched . . . .” Encourage students to challenge each other when they disagree.
Advances Conversing, Listening
Required Materials
Materials to Copy
Rectangle Sort Cards
Required Preparation
Cut out rectangle cards from the blackline master. Each group of 4 needs 1 set of cards.
Launch
Groups of 4
Give each group a set of cards.
Draw or display a rectangle:
[IMG]
“Tell your partner two things you know about this shape.” (There are 4 sides. It looks like a door. It is a rectangle. It is long and flat.)
30 seconds: quiet think time
30 seconds: partner discussion
Share and record responses.
If needed, ask “What is the name of this shape?”
30 seconds: quiet think time
“This shape is a
rectangle
.”
Activity
“Work with your group to sort the shapes into two groups. Put the shapes that are rectangles on the left side of your page. Put the shapes that are not rectangles on the right side of your page. When you place a shape, tell your group why you think the shape belongs in that group.”
4 minutes: small-group work time
“Write a number to show how many shapes are in each group.”
1 minute: independent work time
“Which group has fewer shapes? How do you know?”
30 seconds: quiet think time
30 seconds: partner discussion
Student Facing
Let’s put the shapes into 2 groups.
Rectangle
[IMG]
[IMG]
[IMG]
Not a Rectangle
[IMG]
[IMG]
Student Response
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Advancing Student Thinking
If students put shapes other than rectangles into the group of rectangles, consider asking:
“How did you choose which group to put this shape in?”
“What is alike, or the same, about all of the shapes in this group?”
Activity Synthesis
Invite 1–2 groups to share how they sorted the shapes.
Draw or display a square:
[IMG]
“Which group did you put this shape in?” (We put it with the rectangles because it has 4 sides. We didn’t put it with the rectangles because it is a square.)
“This shape is a
square
, which is a special rectangle because all four sides are the same length.”


correct_option_index: 7