Measure in Halves and Fourths of an Inch

10 min

Teacher Prep
Required Preparation
  • Each group of 2 needs the rulers from the previous lesson.
  • Cut out a ruler from the blackline master for each student.

Narrative

The purpose of this Warm-up is to elicit the idea that a ruler can be marked with halves and fourths of an inch, which will be useful when students use a ruler like this in a later activity. While students may notice and wonder many things about these rulers, focus the conversation on how the quarter-inch marks are distinguished from the half-inch and whole-inch marks. 

Launch

  • Groups of 2
  • Make sure each group has rulers from the previous lesson.
  • Give each student a ruler from the blackline master.
  • “What do you notice? What do you wonder?”
  • 1 minute: quiet think time
Teacher Instructions
  • “Discuss your thinking with your partner.”
  • 1 minute: partner discussion
  • Share and record responses.

Student Task

Look at the rulers you have been using to measure and the ruler your teacher gave you.

What do you notice? What do you wonder?

Solution Steps (2)
  1. 1
    Compare hand-partitioned rulers to standard ruler
    →Notice marks for whole inches, halves, and fourths have different lengths
  2. 2
    Observe precision differences
    →Standard ruler has consistent, precise markings vs hand-drawn marks

Sample Response

Students may notice:

  • On both rulers, the whole-inch marks are the longest.
  • On the rulers we partitioned, the marks we added were not always the same length and not always precise.
  • On this ruler, the marks for halves are all the same length and the marks for fourths are all the same length.
  • The half-inch marks are a little longer than the one-fourth and three-fourth marks.
  • The spacing on the new ruler is very precise.

Students may wonder:

  • Why are some of the marks shorter and some are longer?
  • Are all of the marks in between the whole numbers fourths?
  • How would I use this ruler to measure?
  • What would be the length of something that was in between marks?
Activity Synthesis (Teacher Notes)
  • “How is this ruler like the rulers you used in earlier lessons?” (They all have marks showing whole inches and are partitioned into smaller parts.)
  • “How is it different than those rulers?” (We had one ruler showing fourths of an inch and one showing half inches. On this ruler, both halves and fourths are shown. The marks for whole inches and half inches are different from those for fourth inches.)
  • “On these rulers, the location of 0 is shown with a label. On some other rulers, there’s no gap between the edge of the ruler and the 0, so the edge itself is the 0. Before you use a ruler to measure, it’s good to look at the ruler and check where the 0 is located.”
  • Consider showing students a ruler where one edge of the ruler marks the location of 0, if available.
Standards
Building Toward
  • 3.MD.4·Generate measurement data by measuring lengths using rulers marked with halves and fourths of an inch. Show the data by making a line plot, where the horizontal scale is marked off in appropriate units— whole numbers, halves, or quarters.
  • 3.MD.B.4·Generate measurement data by measuring lengths using rulers marked with halves and fourths of an inch. Show the data by making a line plot, where the horizontal scale is marked off in appropriate units–-whole numbers, halves, or quarters.

15 min

25 min