Part 1: Find the difference. Most of these facts are from Zone 2 (single digit minuend). Work on one column at a time. Part 2: First, study all the facts in rows A-G. Use your pencil to point to each problem as you study, but do not write anything down yet. The difference for all of these problems will be 1, 2, or 3. Next, when you are ready, quiz yourself. See if you can write the answers to all 15 problems in less than 30 seconds.