Midamos con una cinta rota
In earlier lessons, students used rulers, measuring tapes, yardsticks, and meter sticks to measure lengths in inches, feet, centimeters, and meters. They learned that length units are represented on these tools as the length between tick marks. They learned that if they line up the edge of an object with zero on their tools, they can easily read the measurement from the tool without counting each length unit.
In this lesson, students extend their experiences with measurement to include situations when they can not use a tool to measure from 0. They know from prior experience that simply moving an object in space does not change its length (conservation of length). However, this understanding is challenged when students see an object that is not lined up with 0 on a measuring tool. Throughout the lesson, students are encouraged to make sense of and use equations that represent the measuring problems in each task (MP2). This understanding will support learning in future units with representing addition and subtraction on the number line.
- Action and Expression
- Determine the measurement of an object with a measuring tool when the endpoint does not line up with 0.
- Midamos sin empezar en el 0.
Materials to Gather
- Each group of 2 needs access to several objects between 2–10 inches long. Consider using classroom objects such as markers, colored pencils, paperclips, or other objects or images used in previous activities.
|Activity 1||15 min|
|Activity 2||20 min|
|Lesson Synthesis||10 min|
Teacher Reflection Questions
- Capture Squares (1–3), Stage 4: Subtract within 20 (Supporting)
- Math Stories (K–2), Stage 5: Tape Diagrams (Supporting)