1.NBT.4

=Number and Operations in Base Ten=

1.NBT.4 - Add within 100, including adding a 2-digit number and a 1-digit number, and adding a 2-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 2-digit numbers, one adds 10s and 10s, 1s and 1s; and sometimes it is necessary to compose a 10.
 * Use Place Value understanding and properties of operations to add and subtraction**