# Numbers and Operations in Base Ten

## Contact(s)

Judith Spitzli
515-402-8600

Iowa Core Mathematics Documents

Iowa Core Mathematics Support - Resources to support Iowa Core Mathematics.

## Understand place value.

• 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).
• 2.NBT.A.2 Count within 1000; skip-count by 5s, 10s, and 100s.
• 2.NBT.A.3 Read and write numbers to 1000 using base-ten numerals, number names, and expanded form.
• 2.NBT.A.4 Compare two three-digit numbers based on meanings of the hundreds, tens, and ones digits, using >, =, and < symbols to record the results of comparisons.

## Use place value understanding and properties of operations to add and subtract.

• 2.NBT.B.5 Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
• 2.NBT.B.6 Add up to four two-digit numbers using strategies based on place value and properties of operations.
• 2.NBT.B.7 Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
• 2.NBT.B.8 Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.
• 2.NBT.B.9 Explain why addition and subtraction strategies work, using place value and the properties of operations.1

1 Explanations may be supported by drawings or objects.

Printed from the Iowa Department of Education website on April 16, 2014 at 6:44am.