Lesson 11

The purpose of this Estimation Exploration is to practice the skill of making a reasonable estimate for a number based on its location on a number line. Students give a range of reasonable answers when given incomplete information. They have the opportunity to revise their thinking as additional information is provided. The synthesis should focus on discussing what other benchmarks (multiples of 10) would help make a better estimate. The actual number is revealed in the launch of Activity 1.

This estimation exploration encourages students to use what they know about place value to determine the value of the two tick marks the point lies between and then reason about where it is located between them (MP7).

• Groups of 2
• Display the image.
• “What number is represented by the point?”
• “What is an estimate that’s too high?” “Too low?” “About right?”
• 1 minute: quiet think time
• 1 minute: partner discussion
• Record responses in the table.

• “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.

• “What information would help you make a more precise estimate?” (Additional tick marks or other numbers around the point)
• Consider providing new information. “Would you like to revise your estimates?”
• Record new or revised estimates.
• “How did the additional numbers help you revise your estimate?”
• “What other information would you need to be more confident with your estimate?”

The purpose of this activity is for students to use their understanding of place value and the relative position of numbers within 1,000,000 to partition and place numbers on a number line. Students place four related numbers on a number line and consider relationships between digits to determine how to partition a number line.

The numbers have the same non-zero digits but with different place values, allowing students to observe the closely related values of the tick marks (MP7) and the identical location on the different number lines of the numbers they plot (MP8).

• Groups of 2
• “What do you notice and wonder about the first four number lines?”
• 30 seconds: quiet think time
• 30 seconds: partner discussion
• “Think about where you would place the first number on the number line.”
• “Explain to a partner how you decided where to place the number.”

• 10 minutes: independent work time
• 3 minutes: partner discussion
• Monitor for students who:
  • add tick marks to show the halfway mark, and the labeled number slightly less than half on each number line in the first problem
  • label the seventh tick mark on each number line for the second problem

• Ask 2–3 students to share their responses and their reasoning for each problem.
• “How did you partition the number line in the first problem?” (I know that 350 is halfway between 300 and 400, so I marked the halfway point, and then estimated where 3 down from that would be.)
• “How do the number lines help you to see the relationship between the numbers?” (The number lines have endpoints that are ten times as much as the number line before. Also, each number is ten times as much as the number before. The place values changed, but the numbers are located in the same relative position.)

In this activity, students place a set of numbers that are each ten times as much the one before it on the same number line. In doing so, they notice the impact of multiplying a number by ten on its magnitude. Unlike before, the number lines here have no or fewer intermediate tick marks, prompting students to think about how to partition the lines in order to facilitate plotting their assigned number.

• Groups of 4
• Assign each student in a group a letter A–D.

• “Take a few quiet minutes to think about where your assigned number should go on the number line.”
• “Then, discuss your thinking with your group and work together to locate all four numbers on the number line.”
• 3–4 minutes: independent work time
• 7–8 minutes: group work time
• Monitor for students who:
  • partition the number line into hundred-thousands or ten-thousands
  • use benchmarks such as 50,000, 200,000, or 350,000

• Ask 2–3 small groups to share their number line.
• Ask questions about structure:
  • “How did you decide to partition the number line?” (I partitioned the number line by tens, hundreds, thousands, ten-thousands, hundred-thousands—not by ones.)
• Ask questions about precision:
  • “Which numbers were easier to locate? Why?” (34,700 and 347,000, were easier to locate because they were further away from zero.)
  • “What would have made it easier to locate the other numbers?” (A longer number line would have made it easier to include more partitions)
• Ask questions about magnitude:
  • “Make some observations about where the numbers are positioned on the number line.” (Most of the numbers we located are much closer to zero than to 400,000)
  • “You located the same four numbers here as you did in the first activity. How are the locations of the points different from those in Activity 1?” (Sample response: Ten times as much looks different when they are all on the same number line.)