NC.4.NBT.4

Students build on their conceptual understanding of addition and subtraction using place value and flexibility with multiple strategies including expanded form and drawings of base 10 blocks to make sense of the standard algorithm. 

Students are expected to explain their thinking to show understanding of the algorithm. They will use place value in describing and justifying the processes they use to add and subtract.  In mathematics, an algorithm is defined by its steps and not by the way those steps are recorded in writing. With this in mind, minor variations in methods of recording standard algorithms are acceptable. Fourth grade is the first time students are expected to be proficient at using the standard algorithm to add and subtract. 

NOTE: Students may ask if it is possible to subtract a larger number from a smaller number. While it is not the focus or expectation of this standard in this grade, students should know that it is mathematically possible, and they will be learning more about that concept in later grades. If the misconception that larger numbers cannot be subtracted from smaller numbers is confirmed or reinforced, students may struggle to make the transition to negative numbers in later grades.