Grade 1 · Number and Operations in Base Ten

CCSS.MATH.CONTENT.1.NBT.C.4

Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, 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 and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.

Read this standard on the official Common Core site

Lessons that teach this standard

• Adding Tens and Ones Within 100

  First grade: find 10 more or 10 less in your head, add and subtract tens, and add within 100 by adding tens to tens and ones to ones, making a new ten when needed.