## Lesson: Estimating and Measuring Amounts Introducing the Concept

In this lesson, students explore nonstandard and standard units of measurement. They will learn why some nonstandard units are unreliable, while standard units, whose lengths remain constant, are useful.

Materials: Houghton Mifflin Math, Pupil Edition; ten crayons; centimeter ruler (Learning Tool 24 in the Learning Tools Folder) for each group of students

Preparation: Organize crayons in groups of 10 according to length. The crayons in each group should be about the same length (for example, one group of 10 new crayons; one group of 10 used crayons, each about 5 centimeters long; and so on). Distribute the crayons and math books. Cut out or have students cut out the centimeter rulers.

Prerequisite Skills and Concepts: Students should understand the concept of measurement and know that a centimeter is a unit of linear measurement.

• Say: We're going to use crayons to measure the length of our math books.
Point to the spine of a math book when you say length of our math books.
• Say: Line up the end of one crayon with one end of the book.
Observe students to ensure that they understand this instruction, or demonstrate it for them.
• Say: Now place more crayons end-to-end alongside your math book.
As students are working, point out to them that the last crayon may extend somewhat beyond the end of the book or fall just short of the end of the book.