In this activity, students first measure colored pencils to the nearest inch, collect a set of data in a table, and then plot the data on a number line. Then they measure the colored pencils again, but this time to the nearest  inch. They plot their data on a new number line and attend to a greater level of precision as they do so. Students then reflect on the difference in the measuring process and in the measurements on the same set of pencils. Students attend to precision when they measure the pencils to the appropriate fractional unit (MP6).

• Allow students to record their two sets of data on two different class line plots. (If dot stickers are available, consider using them—one sticker for each data point.)
• “How did your data and line plots change when you measured the pencils to the nearest inch?” (We got different numbers. The marks or points on the line plots are spread out differently. The points for some of the same pencils show up as different lengths in the second line plot.)
• “What is challenging about measuring to the nearest inch?” (The tick marks are smaller and harder to see on the ruler.)
• “Why do you think we measure to the nearest inch?” (We measure to be more accurate.)
• “Let’s look at some other length data with measurements in halves, fourths, and eighths of an inch.”

In this activity, students create a line plot using measurements to the nearest inch and nearest inch. This task prompts students to use their understanding of fraction equivalence to plot and partition the horizontal axis.

• “How many pencils were measured in Andre’s class?” (10, because there were 10 data points and each represented a pencil that was measured.)
• “What was the most common measurement in the first set of data? In the second set of data?” (In the first set of data: inches. In the second set of data: inches.)
• “How did you use equivalence to help as you plotted measurement data in eighths of an inch?” (I know that 2 eighths are equivalent to 1 fourth, and this helped me find eighths on the line plots.)
• Use the line-plot image to clearly label , , and , with help from students.

In this activity, students continue to analyze line-plot data and use the data to answer questions. Each data set involves lengths measured to the nearest inch and inch. As students organize and analyze data, they revisit ideas about fraction equivalence and addition and subtraction of fractions. When students relate the data to the context it represents and carefully interpret the elements of a graph, they reason abstractly and quantitatively and attend to precision (MP2, MP6). 

• Select students to share strategies for finding the difference between the longest and shortest lengths? 
• Make connections between strategies, being sure to emphasize strategies that involve decomposing fractions in different ways. 
• Consider asking: “What are the similarities between these strategies?”