Find the difference 921 - 578 using the same change algorithm. Lesson: If a subtraction problem is of the form "big minus small\" in every place value, no adjustments need to be made. But school children are not expected to perform subtractions in the form "small minus big.\" Several methods are use to change "small minus big" to "big minus small.\" The most popular method is incorrectly called "borrowing.\" When you borrow something, you are expected to put it back. So the proper name is "regrouping.\" Below we outline a second method called the same change algorithm. Step 1. Add a single digit number (such as 3, 4, 5, etc.) to both the minuend and subtrahend so that the ones place in the subtrahend is zero. Record this after the first arrow. Remember, the subtrahend must have a zero in the ones place. Step 2. Add a multiple of ten (such as 30, 40, 50, etc.) to both the minuend and subtrahend so that the tens place in the subtrahend is zero. Record this after the second arrow. At this point the subtrahend should end in two zeros. Step 3. Find and record the difference. Subtrahend must Subtrahend must end with one zero end with two zeros J 8 921 - - 578 ~ ~