# Lesson 2

## Warm-up: True or False: Multiples of Ten (10 minutes)

### Narrative

The purpose of this True or False is to elicit strategies students have for multiplying a one-digit number by a multiple of ten. The reasoning students do here helps to deepen their understanding of the properties of operations and develop fluency.

When students use place value or properties of operations as strategies to divide, they look for and make use of structure (MP7).

### Launch

• Display one equation.
• “Give me a signal when you know whether the equation is true and can explain how you know.”
• 1 minute: quiet think time

### Activity

• Share and record answers and strategy.
• Repeat with each equation.

### Student Facing

Decide if each statement is true or false. Be prepared to explain your reasoning.

• $$3\times60=9\times10$$
• $$180=3\times60$$
• $$6\times40=24\times10$$
• $$24\times10=240$$

### Activity Synthesis

• “How can you explain your answer without finding the value of both sides?”
• “Who can restate _____’s reasoning in a different way?”
• “Does anyone want to add on to _____’s reasoning?”

## Activity 1: Card Sort: Triangles (15 minutes)

### Narrative

The purpose of this activity is for students to sort triangles into more specific categories. This requires students to attend to an attribute other than the number of sides. As students sort the triangles, monitor for students who sort by the number of equal side lengths or the presence of a right angle (MP7). Although the terms “equilateral,” “isosceles,” and “scalene” are not introduced in this lesson it is fine if students already know them and use them to describe the groups of triangles.

MLR2 Collect and Display. Direct attention to words collected and displayed from the previous lesson. Invite students to borrow language from the display as needed, and update it throughout the lesson.
Representation: Access for Perception. Synthesis: Use gestures during explanation of triangle sorting to emphasize side lengths of triangles.
Supports accessibility for: Visual-Spatial Processing

### Required Materials

Materials to Copy

### Required Preparation

• Create a set of cards from the blackline master for each group of 2 or 4.
• When copying the card sort triangles, use colored paper to distinguish these cards from the cards in the next activity.

### Launch

• Groups of 2 or 4
• Distribute one set of pre-cut cards to each group of students.
• “What do you notice about the shapes on the cards?” (The shapes are all triangles. They all look different. Some of them have sides that are the same length.)
• 1 minute: quiet think time

### Activity

• “Work with your partner to sort the triangles into categories. Be sure to explain your categories.”
• 8 minutes: partner work time
• Monitor for students that sort the triangles into groups based on:
• the number of sides with equal length (all, two, none)
• the sides and corners having the same size (the triangles being identical)
• the presence of right angles

### Student Facing

Sort the triangles into categories. Record your categories and be prepared to explain how you sorted the shapes.

### Student Response

If students say they aren’t sure how to sort the shapes because they are all triangles, consider asking:

• “What other attributes have you used before to sort shapes?”
• “How are some of the triangles different?”

### Activity Synthesis

• Select groups to share their categories and how they sorted their cards.
• Allow as many categories to be presented as time permits, but be sure to highlight categories based on the number of sides with equal length.
• Highlight the use of terms like “equal side lengths” and “angles.”
• Record and display the attributes students use to categorize the triangles.

## Activity 2: Card Sort: Quadrilaterals (20 minutes)

### Narrative

The purpose of this activity is to sort quadrilaterals by their attributes. By now students may be inclined to look for sides of equal lengths and for right angles. They may not look for parallel sides (and are not expected to know the term “parallel”), but may notice that some quadrilaterals have pairs of sides that are oriented in the same direction (MP7). Encourage students to describe such observations in their own words.

The quadrilateral cards from this activity will be used in the next lesson and in centers.

### Required Materials

Materials to Gather

Materials to Copy

### Required Preparation

• Create a set of cards from the blackline master for each group of 2 or 4.
• Bags or envelopes can be used to store sets of cards from this activity for use in the next lesson.

### Launch

• Groups of 2 or 4
• Distribute one set of pre-cut cards to each group of students.
• “What do you notice about the shapes on this set of cards?” (There are 20 shapes. All the shapes are quadrilaterals. Some have right angles and some don’t.)
• 1 minute: quiet think time

### Activity

• “Just like the last activity, sort cards into categories that you and your partner choose.”
• 8 minutes: partner work time
• Monitor for different attributes that students use to sort the shapes.

### Student Facing

Sort the quadrilaterals into categories. Record your categories and be prepared to explain how you sorted the shapes.

### Activity Synthesis

• “Display your sorted cards so that others can see them.”
• “Visit another group’s cards and see if you can figure out how they sorted their quadrilaterals. Be prepared to share your reasoning.”
• 2–3 minutes: Students visit other groups’ displays.
• Invite each group to share how the cards were sorted and their reasoning. Record and display the attributes students use to categorize the quadrilaterals.
• Attend to the language that students use to describe the categories and shapes, giving them opportunities to describe the shapes more precisely.
• Highlight the use of terms like “equal sides” and “right angles.”

## Lesson Synthesis

### Lesson Synthesis

“Today we sorted triangles and quadrilaterals into more-specific categories.”

Display the two compiled lists of attributes used to sort triangles and quadrilaterals.

“Which attributes did we use to sort both sets of shapes?” (The number of sides of the same length. The number of right angles. Whether there were pairs of sides that go in the same direction.)

“Which attributes did we use for one set of shapes but not the other? Why might that be?” (In quadrilaterals we counted the number of right angles, but in triangles we just sorted by whether they had one or not. This is because triangles could only have 1 right angle. We looked at pairs of sides that go in the same direction when sorting quadrilaterals but not when sorting triangles. The sides of triangles can’t go in the same direction.)