The Language of Estimation

Explicit Instruction/Teacher modeling

• Ask students to think about what tools are needed to measure something. Allow a few students to share out their ideas. Take out a ruler and explain to the students that the ruler is 12 inches long, or one foot. Elaborate that one foot is equal to 12 inches. Explain to the students that if we don't want to use a ruler to measure the exact length of something, we can estimate instead.
• Explain to the students that we use important words and phrases to explain our estimates to others, and they will learn some of these words on the vocabulary cards.
• Put students in partnerships and pass out copies of the Vocabulary Cards and personal whiteboards and whiteboard markers to each pair. Project your copy of the Vocabulary Cards on the whiteboard.
• Read the definition of estimate on the vocabulary cards and refer to the visual to support student understanding. Provide relevant examples of situations when someone might estimate something (e.g. figuring out how much money items cost at the store, how long it will take to get somewhere, if a couch will fit in a living room, a picture to hang on the wall, etc.) Explain to the students that today they will be using a nonstandard unit of length, a giant sneaker, to estimate the length of the reading area where you want to put the rug.
• Read through the rest of the vocabulary cards. Pause after reading each word and have students complete a think-pair-share, defining each vocabulary word in their own words.
• Assign each partnership one or two vocabulary words. Ask students to come up with a sentence and record it on their personal whiteboard.
• Jot down student sentences on the whiteboard and clarify any misconception of tricky words like about and close, and provide example sentences for students.

Guided Practice

• Project the Estimate with a Giant Sneaker worksheet on the whiteboard and pass out the pre-cut giant sneakers to each partnership.
• Hold up a giant sneaker and say, "I'm going to estimate the length of the reading area using this giant sneaker. First, I notice that the giant sneaker is almost the size of a ruler." Hold up the sneaker next to the ruler to show students what you mean.
• Model figuring out the length of the reading area by referencing your giant sneaker. For example, place the sneaker on the ground to figure out the length of the reading area. Say, "I'm going to place this sneaker here, right against the wall (bookshelf, chair, etc). Next, I'm going to put my finger down at the end of the sneaker. I will keep my finger on the ground and move the sneaker to the other side of my finger. I want to make sure the sneakers are side to side, not overlapped. This will make my estimate more accurate, or close to the real measurement. I can continue placing the sneakers side by side until I feel comfortable making an estimation."
• Continue this process until you are about half way across the reading area. Count the number of sneakers aloud, pointing and saying each number aloud to the students. Make an estimation of the reading area by saying, "I think the length of the reading area is about ____ sneakers. I know the sneakers are almost the same size as a ruler, so I think the reading area is about ____ feet."

Group work time

• Write the following statements on the whiteboard:
  • The length of a desk is closer to 10 sneakers than one sneaker.
  • The length of the door is about one sneaker, not 10 sneakers.
• Ask for a student to share the definitions of the vocabulary words in each statement (closer and about). Clarify any misconceptions and reiterate the meaning of both words by referencing the Vocabulary Cards worksheet.
• Instruct students to record the two statements in their math journals. Explain to the students that you came up with these estimations, but you need help figuring out if they are correct or incorrect.
• Have students work in partnerships to estimate the length of the desk and the door, referring to their sneakers to figure out their answers. Tell students to record their answers in their math journals, using pictures, words, phrases, and sentences. Provide sentence frames to support students as they record their answers, such as:
  • I agree/disagree that the length of a desk is closer to 10 sneakers because ____. I think the length of a desk is closer to ____ sneakers because ____.
  • I agree/disagree that the length of the door is about one sneaker because ____. I think the length of the door is closer to ____ sneakers because ____.
• Rotate around the classroom as students are solving the problems and guide students as needed.