Lesson 6

This warm-up prompts students to compare four images. It gives students a reason to use language precisely (MP6). It gives the teacher an opportunity to hear how students use terminology and talk about characteristics of the items in comparison to one another. During the synthesis, ask students to explain the meaning of any terminology they use, such as parts, partitions, mark, label, thirds, or fourths.

• Groups of 2
• Display the image.
• “Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”
• 1 minute: quiet think time

• “Discuss your thinking with your partner.”
• 2–3 minutes: partner discussion
• Share and record responses.

• “To make your reasoning clear while locating and labeling fractions on a number line, what are some important things to include?” (Partitions of the equal parts, a dot and label at the fraction.)
• “We learned in a previous lesson that we label fractions on the number line at the tick marks just like we have labeled whole numbers on the number line.”
• “How is this different from how we labeled our fraction strips like in A?” (In diagrams of fraction strips we labeled the part that has size or length \(\frac{1}{3}\). On the number line we are labeling the number \(\frac{1}{3}\).)

The purpose of this activity is for students to make sense of partitioning number lines that extend beyond one. Clare and Diego's work surfaces 2 common misconceptions that students often make while partitioning number lines into fractions. Clare partitions the entire number line into fourths and Diego places 4 tick marks to show fourths. Students analyze these misconceptions (MP3) before they locate and label unit fractions on number lines of various lengths in the next activity.

• Groups of 2
• “Today we are going to partition number lines to locate unit fractions. Take a minute to look at how Clare, Andre, and Diego have partitioned their number lines into fourths.”
• 1–2 minutes: quiet think time

• “Work with your partner to decide whose partitioning makes the most sense to you and why.”
• 3–5 minutes: partner work time
• Monitor for students who can explain why Andre’s partitioning makes sense and why the others do not show fourths.

• Ask students to share why Andre’s partitioning makes sense to them.
• Consider asking:
  • “Did anyone think of Andre’s reasoning in a different way?”
  • “How do we know that Andre’s number line is partitioned into fourths?”
• Ask students to explain why Clare and Diego’s partitioning does not show fourths.
• “We learned that when you partition the number line, you have to pay attention to where 0 and 1 are and make sure to partition that into the right number of equal-length parts.”

The purpose of this activity is for students to partition the interval from 0 to 1 into equal parts to locate and label unit fractions. Students see number lines that vary in length, from 1 unit to 4 units, which provides an opportunity for them to practice accurately partitioning the unit on the number line, rather than the entire number line (MP6). Some number lines show numbers greater than one which gives students the opportunity to think about fractions greater than one even though they are not explicitly addressed in this lesson.

• Groups of 2
• “Now that we’ve thought about some common mistakes about partitioning number lines, you are going to have a chance to partition number lines to locate and label unit fractions.”

• “Work independently to partition each number line and locate and label each fraction.”
• 3–5 minutes: independent work time
• “Now, share how you partitioned each number line and where you located and labeled each fraction with your partner.”
• “Be sure to share tips on how you partitioned or ask for tips for any of the partitions that were challenging.”
• 3–5 minutes: partner discussion
• Monitor for students who disagree on how to partition one of the number lines.

• “Tell me about how you partitioned your number line.”
• “What did we learn in the last activity about how to partition number lines?”

• “Were there any number lines that you and your partner were not sure how to partition or disagreed about? How did you resolve your confusion or disagreement?” (We weren’t sure how to partition the number line that goes up to 4 when we were locating \(\frac{1}{2}\). We talked together about partitioning just the space from 0 to 1 into half.)
• Consider asking: “What was different about partitioning, locating, and labeling fractions on number lines with numbers greater than 1 than on number lines that just go up to 1?” (You have to be careful to just partition the one whole, not the whole number line.)
• Display the same unit fraction on a number line with length 1 and length 2, such as:

• “What do you notice?” (The top number line just has 0 to 1. The bottom number line has the 0 to 2. The number 1 is located in the same place on both number lines. The number \(\frac{1}{6}\) is located in the same place on both number lines.)
• “The location of any number on the number line doesn’t change just because we extend the number line. The number \(\frac{1}{6}\) is located between 0 and 1 whether the number line goes up to 1 or it goes up to another number.”