Lesson 6

The purpose of this lesson is to measure length by iterating same-size length units with no gaps or overlaps.

In the previous lesson, students used connecting cube towers to measure length. In this lesson, students use paper clips to measure. Since these length units are not connected, students need to make sure that there are no gaps or overlaps when they line them up. In the first activity, students use paper clips to measure the length of a rectangle and discuss how measuring with paper clips is the same and different as measuring with connecting cubes. In the second activity, students analyze three measurements of the same object and determine which is correct and why. This discussion helps deepen students understanding of length as a continuous measure of length units, not merely a count of objects in a line. In the third activity, students practice measuring different lengths using paper clips.

• Each group of 2 needs about 30 1-inch paper clips.

• Put strips of tape of the designated lengths on the floor. Label each strip. There should be one strip of tape per group.
  • Tape A: 18 inches
  • Tape B: 16 inches
  • Tape C: 12 inches
  • Tape D: 20 inches
  • Tape E: 22 inches
  • Tape F: 25 inches

As students measured with length units that do not connect, what evidence did you see that students understand why leaving gaps or overlapping units results in an inaccurate measurement of an object’s length?