# 2.NBT.A.1*

Understand that the three digits of a three-digit number represent amounts of hundreds, tens, and ones; e.g., 706 equals 7 hundreds, 0 tens, and 6 ones. Understand the following as special cases:
 - 100 can be thought of as a bundle of ten tens — called a “hundred.” - The numbers 100, 200, 300, 400, 500, 600, 700, 800, 900 refer to one, two, three, four, five, six, seven, eight, or nine hundreds (and 0 tens and 0 ones).

*TNCore Focus Standard

## Summary:

The concept of hundreds, tens, and ones is the foundational basis for our base-ten number system. Students should understand that the three digits in a three-digit number represent the number of hundreds, tens, and ones, and that 100 can be thought of as a hundred ones or as ten tens, or as a bundle called a "hundred". The numbers 100, 200, 300, etc, represent one hundred, two hundreds, three hundreds, etc. and no ones or tens.  This skill is built on in each grade and is used in operations on whole numbers. The idea that each digit in a number has a specific value is key to making sense of place-value-based algorithms for operations.  This standard builds on Standard 1.NBT.B.2 and introduces hundreds.

## Understanding the Standard:

• Remind students of the idea of bundling 10 ones to make one ten. Then expose students to the idea of bundling 10 tens to make one hundred.
• Help students build on their recognition that two-digit numbers are composed of a certain number of tens and an appropriate number of ones.
• Provide students with problems/opportunities to think of and verbalize the numbers 100, 200, ..., 900 as a certain number of hundreds and 0 tens and 0 ones. Use pictures of rods to help students visualize this concept.
• Provide students with manipulatives and technologies to represent three-digit numbers. This will allow students to physically make bundles of tens and hundreds and to understand the value of each digit in a three-digit number, helping them develop a concrete understanding of an abstract concept.
• There are two directions in which students should be able to move from a numeral (325) to a representation of the number (a verbalization such as "three hundreds, two tens, and five ones" or using base-ten blocks or drawings), and from a representation to a numeral.

## Questions to Focus Instruction:

• Can students bundle a group of 10 tens into a hundred and understand that 10 tens and a hundred are equal?
• Do students understand that the thee digits in a three-digit number refer to the number of hundreds, tens, and ones?
• Can students verbalize the number of hundreds, tens, and ones represented by three-digit numbers?
• Do students understand that 100, 200, and so on, refer to a certain number of hundreds (and 0 tens and 0 ones)?
• Can students explain their reasoning when indicating how many ones, tens, and hundreds a number has?
• Can students move from a numeral (325) to a representation of the number (a verbalization such as "three hundreds, two tens, and five ones" or using base-ten blocks or drawings), and from a representation to a numeral?

## Skills

Prior to: Students can represent any two-digit number, recognizing that they are composed of a certain number of tens and an appropriate number of ones. Go to 1.NBT.B.2b. to see previous skills in this progression.

At Grade Level: Students will use their knowledge of bundling to bundle ten tens to make a hundred.

Moving Beyond:
Students’ mastery of regrouping will be demonstrated as they add and subtract through 1000 with numbers having as many as four-digits. Some of these problems will require them to use their knowldege of regrouping (2NBT.7). Students will also generalize the idea of place value, understanding that in a multi-digit number, each place represents a vlaue ten times the value of the place to its right (4.NBT.1).