Lesson 5

The purpose of this lesson is for students to use their understanding of length and the structure of a number line to estimate the location of a number on a number line.

In previous lessons, students estimated the length of objects using what they know about the size of standard length units and the tools used to measure them. Students have located numbers on number lines using what they know about the structure of a number line and the labeled tick marks.

The purpose of this lesson is for students to extend this understanding by estimating numbers on number lines that do not have tick marks to represent each consecutive whole number. Students use their understanding of length and unit intervals on the number line to estimate. Students should be encouraged throughout the lesson to explain why their estimates are reasonable using what they know about number, length, and the structure of the number line.

• Create a number line on chart paper for each group of students. 
• On each number line, draw tick marks at the beginning (label 0) and the end (label 40)
• On each number line, draw tick marks and label: 10, 20, 30.
• Create a set of number line cards from the blackline master for each group of 3 (each set should include 10 cards).

What strategy did most students use when locating a number on a number line without the support of the tick marks? How can you support students to assess the reasonableness of their estimates in future lessons?