Start by asking your students which blue line is longer:
Answer: They're the same length!
Next, ask which horizontal line is longer:
Answer: The horizontal line on the right is much longer!
After that, students will learn how to determine how much longer or shorter something is than another.
Conclude by giving your students some of these puzzles.
Measure lengths 2 by Khan Academy
Conclude by leading this investigation:
2.MD.A.1: Measure the length of an object by selecting and using appropriate tools such as rulers, yardsticks, meter sticks, and measuring tapes.
2.MD.A.4: Measure to determine how much longer one object is than another, expressing the length difference in terms of a standard length unit.