2.4 Addition and Subtraction on the Number Line

Unit Goals

  • Students learn about the structure of a number line and use it to represent numbers within 100. They also relate addition and subtraction to length and represent the operations on the number line.

Section A Goals

  • Represent whole numbers within 100 as lengths from 0 on a number line.
  • Understand the structure of the number line.

Section B Goals

  • Represent sums and differences on a number line.
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Glossary Entries

  • bar graph
    A way to show how many in each group or category using the length of rectangles.
  • centimeter

    A length unit in the metric measurement system. There are 100 centimeters in a meter.

  • compose
    To make a new unit from 10 of the next smallest unit. For example, compose a ten from 10 ones.
  • data
    Information about the things or people in a group.

    Example: If you have a box of colored pencils, then the lengths and colors of each of the pencils are data about the pencils in the box.
  • decompose
    To break a unit into 10 of the next smallest unit.  For example, decompose a ten into 10 ones.
  • foot

    A length unit in the U.S. customary measurement system.

    There are 12 inches in a foot.

  • inch

    A length unit in the U.S. customary measurement system. 

    There are 12 inches in a foot.

  • line plot
    A way to show how many of each measurement using an x for each measurement.
  • meter

    A length unit in the metric measurement system. 

    There are 100 centimeters in a meter.

  • number line

    A diagram that represents numbers as lengths from 0 using equally spaced tick marks or points.

  • picture graph
    A way to show how many in each group or category using pictures of the objects or symbols.