Lesson 3

The purpose of this lesson is for students to use base-ten representations to build an understanding of the digits in three-digit numbers.

In previous units, students used base-ten blocks and diagrams to compose and decompose tens when adding and subtracting by place. In previous lessons, students learned that a hundred is a unit that is made up of 10 tens and used base-ten blocks to show composing a hundred with 10 tens.

In this lesson, students represent three-digit numbers that include an amount of hundreds, tens, and ones. In the first activity, students take inventory of the units represented by a collection of base-ten blocks. They use their understanding of the units of hundred and ten to determine how to represent the total value with the fewest number of blocks possible. In the second activity, students use base-ten diagrams to represent values using the fewest number of each unit possible and connect these representations to the meaning of each digit in a three-digit numeral. In both activities, look for the different ways students represent and record the value of their blocks for reference in the activity syntheses and in future lessons.

• Each group of 3–4 students will need a container with 2 hundreds, 28 tens, and 15 ones.
• Each group of 3–4 students will need access to additional base-ten blocks (hundred blocks and ten blocks).

In grade 1, students developed an understanding of the digits in a two-digit number. How did the work of this lesson reinforce that understanding? How did it build on that understanding?