Invented Strategies - Partial Differences

In this method, students use the expanded form of numbers to create simpler subtraction problems and avoid regrouping.  One of the most common problems students face in solving problems is that they want to begin on the left and work to the right.  In the traditional regrouping method, this is not possible and leads to errors.  In the partial difference method, students can work left to right, leading to fewer errors.  The students have enjoyed this method because of the exposure to negative numbers.  If an answer is a negative number, the student puts a minus sign in front of it.  If the answer is a positive number, the student puts a plus sign in front.  Students must be flexible in their thinking and be able to do mental computations.