Students build on their understanding of addition by adding up from the number being subtracted to the whole.
Students may count back from the whole to solve the subtraction problem and even more so if the numbers are close. Students may remove the subtrahend in parts (decompose number).
place value & negative numbers
Students break each number into its place value. Like values are grouped and the subtracted. Students may use negative values.
When students begin to understand subtraction is the difference between two numbers, they can begin to change both numbers by the same amount to make the subtraction friendlier.
adjusting one number
Students adjust one number to make the problem more efficient and friendlier. The final answer needs to be adjusted to compensate for the initial change in number.
Students expanded each number according to place value and subtract. This ensures place values stays at the forefront of subtraction and explicitly shows what is occurring in each step of the algorithm.
Students begin to place numbers vertically but continue to explicitly show place value throughout the algorithm.
Students may use the standard algorithm once they have built their understanding of what is taking place throughout.