Lesson 3

This Number Talk prompts students to use place value and properties of operations to multiply single-digit numbers by multiples of ten. The strategies elicited here help students develop fluency.

• Display one expression.
• “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

• Record answers and strategy.
• Keep expressions and work displayed.
• Repeat with each expression.

• “How were you able to use \(4\times40\) to find the other products.” (I doubled \(4\times40\) to find \(8\times40\). Once I knew \(4\times 40\), I could count up or down by 40 to get the other products.)
• Consider asking: “Why might it be helpful to first think of each expressions as multiplying a number and 4 instead of 40?” (We know many multiplication facts for 4, and that 40 is 4 tens. We can think of each problem as groups of 4 tens instead of groups of 40.)

The purpose of this activity is to introduce the game Mystery Quadrilateral and strategically consider the questions that could be asked next to determine a mystery quadrilateral. Students play a round of this game against the teacher. In the next activity, students will play this game in groups of 2.

• Gather a set of quadrilateral cards from the previous lesson.

• “We are going to play a game called Mystery Quadrilateral. Read the directions independently."
• 1 minute: quiet think time

• “Now let’s play a round together. I’ll be Partner A and the class will be Partner B.”
• Play a round of the game.

• “What kinds of questions might help you figure out the mystery quadrilateral?” (Questions about something we didn’t already know about the shape. General questions to narrow down the type of quadrilateral, then more-specific questions to figure out which one.)

The purpose of this activity is for students to practice describing geometric attributes of a quadrilateral with increasing precision by playing a game. Students should be encouraged to ask questions like, “Are all the sides the same length?” rather than, “Is it a square?” to keep the focus on attributes of the quadrilateral rather than the name. As students decide which questions to ask they think about important attributes such as side lengths and angles and have an opportunity to use language precisely (MP6, MP7).

Students will use the quadrilaterals from the previous lesson to hide in the “mystery quadrilateral” folder, but will have a copy of all the shapes in their workbook to support them in asking questions to narrow down the shape. Students can also cover shapes in their workbook with counters as they rule out shapes.

• Each group of 2 needs a set of quadrilateral cards from the previous lesson.
• Each group of 2 will need a folder to hide the card during this activity.

• Groups of 2
• “Now you’re going to play Mystery Quadrilateral with your partner. Re-read the directions for the game, then think about some words that may be helpful as you play.” (side, angle, right angle, equal, skinny, tall, slanted)
• 1 minute: quiet think time
• Share and record responses.
• Give each group a folder containing a set of the quadrilateral cards from the previous lesson.
• “How could you use the images of all the quadrilaterals on your paper as you play?” (They can help me think about questions I could ask. I could mark off quadrilaterals as I figure out that they're not the mystery quadrilateral.)
• Give students access to counters and let them know they can be used to cover shapes they want to cross out during the game.

• “Play Mystery Quadrilateral with your partner. Be sure to take turns hiding the shape and guessing the shape.”
• 10–15 minutes: partner work time

• “What shapes were the easiest to figure out and why?” (W was easy because it was so different with one angle pointing in. X was easy because it was the only square resting on a side.)
• “What shapes were the most challenging to ask questions about and why?” (FF was challenging because none of the sides were the same length, and it was hard to get more information with “yes” or “no” questions. M and BB were hard to tell apart because they were so similar and it was hard to figure out what questions to ask.)