Grade 2 · Number and Operations in Base Ten

CCSS.MATH.CONTENT.2.NBT.B.9

Explain why addition and subtraction strategies work, using place value and the properties of operations.

Read this standard on the official Common Core site

Lessons that teach this standard

• Adding and Subtracting Within 100

  Grade 2: add and subtract within 100 with place value — tens with tens and ones with ones, making a ten, counting up — add up to four numbers, and explain why it works.

• Adding and Subtracting Within 1,000

  Grade 2: add and subtract three-digit numbers — hundreds with hundreds, tens with tens, ones with ones — making or breaking tens and hundreds, and write it in columns.