Lesson 2

The purpose of an Estimation Exploration is to practice the skill of estimating a reasonable answer based on experience and known information. When students notice that they can make a more accurate estimate more readily when the connecting cubes are grouped in towers of 10 they make use of base-ten structure (MP7).

This is the first time students participate in this routine in grade 1. The teacher can begin by saying, “Today we are doing a new warm-up called Estimation Exploration. In this activity we are going to see a collection of objects. Your job is to look at the image and think about how many objects there are.” Let students know that they should estimate, or find a value that is close to the correct value, without counting each one. As needed, clarify that the number they come up with is called an estimate.

• Groups of 2
• Display the first image.
• “What is an estimate that’s too high?” “Too low?” “About right?”
• 1 minute: quiet think time

• “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.
• “Let’s look at another image of the same collection.”
• Display the second image.
• “Based on the second image, do you want to revise or change your estimates?”

• “Let’s look at our revised estimates. Why were these estimates more accurate the second time?” (Some of the cubes are organized. We could see there were more than 2 tens.)
• “There are 30 cubes.”

The purpose of this activity is for students to make connections between representations of multiples of 10. Students match cards that show multiples of 10 with pictures, numbers, and words. Each student is given a card and then moves around the room to find the other two students whose cards have the same value.

During the synthesis, the teacher and students create a chart to display the matches. Students discuss the direct connection between the number, the written number of tens, and the representation of towers of 10. When students notice and describe that the first digit in each number matches the written number of tens and the number of towers of 10, they look for and make sense of the base-ten structure (MP7).

• Create a set of cards from the blackline master for the class. Each student will only need one card.
• Create a large chart titled “Representations of Tens” at the top. Draw three columns. Label columns “Number,” “Number of Tens,” and “Drawing.”

• Groups of 2
• Give each student a card.
• “Today you will play a game in which you try to find cards that match.”
• “To play this game, each of you will get one card. Find the other two students who have cards with the same value. Each time you compare cards with another student, discuss whether or not your cards have the same value and how you know.”

• 5 minutes: partner work time
• If time: Shuffle the cards and have students repeat the activity with new groups.
• As students work, consider asking
  • “How do you know these cards match?”
  • “How many tens does this card have?”

• “Let’s look at the matches we saw during the game today.”
• Write 10 in the first column of the chart.
• “Who has 10? How do you know?”
• Repeat for all multiples of 10, discussing how students know their cards match for each multiple of 10.

The purpose of this activity is for students to connect written multiples of 10 to base-ten representations. Students notice a connection between how the numbers are said, written, and represented with tens. For example, “70” has the word “seven” as it is said, the digit “7” when it is written, and is represented with seven tens. Each number name is written under the number in this activity. Students are not expected to spell number names.

• Groups of 2
• Give each student a blackline master and access to connecting cubes.

• Read the task statement from the blackline master.
• 5 minutes: independent work time
• 3 minutes: partner discussion
• Monitor for students who count the number of towers, match correctly, and can explain how they knew.

• Invite previously identified students to share.
• “How did you know which representations matched?” (I counted by ten and found the number. I said 10, 20, 30, 40, 50, and found 50.)