Relate the addition 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.
Numbers and Operations in Base Ten
- Use place value understanding and properties of operations to add and subtract.
Add within 100 including adding a two-digit number and a one-digit number. Add a two-digit number and a multiple of 10.