Add within 100, including a two-digit number and a one-digit number; a two-digit number and a multiple of 10. Use concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones, and sometimes it is necessary to compose a ten. Relate the strategy to a written representation and explain the reasoning used.
Number and Operations in Base Ten
- Use place value understanding and properties of operations to add and subtract.