Nearest Multiples of 10 and of 100

10 min

Narrative

The purpose of this Estimation Exploration is for students to think about what value a point on the number line could represent. The only labeled tick marks are hundreds, so students need to reason about what numbers are in between and how far the point is from the labeled numbers. 

Launch

  • Groups of 2
  • Display the image.
  • “What is an estimate that’s too high? Too low? About right?”
  • 1 minute: quiet think time
Teacher Instructions
  • “Discuss your thinking with your partner.”
  • 1 minute: partner discussion
  • Record responses.

Student Task

What number could the point on the number line represent?

<p>Number line. Scale 0 to 200 by 100's. Point between 100 and 200.</p>

Record an estimate that is:

too low about right too high

Sample Response

Sample responses:
  • Too low: less than 130
  • About right: 130–140
  • Too high: greater than 140

Synthesis

  • Consider asking:
    • “Is anyone’s estimate less than _____? Is anyone’s estimate greater than _____?”
    • “Based on this discussion, does anyone want to revise their estimate?”
  • “What would help us be more sure of our estimate?” (More tick marks that are equally spaced. Marks of multiples of 10.)
Standards
Building On
  • 2.MD.6·Represent whole numbers as lengths from 0 on a number line diagram with equally spaced points corresponding to the numbers 0, 1, 2, …, and represent whole-number sums and differences within 100 on a number line diagram.
  • 2.MD.B.6·Represent whole numbers as lengths from 0 on a number line diagram with equally spaced points corresponding to the numbers 0, 1, 2, …, and represent whole-number sums and differences within 100 on a number line diagram.
Building Toward
  • 3.NBT.1·Use place value understanding to round whole numbers to the nearest 10 or 100.
  • 3.NBT.A.1·Use place value understanding to round whole numbers to the nearest 10 or 100.

20 min

15 min