A part-part-whole mat is a piece of paper with an oval on it that has been divided into two parts by a dotted line. Students use these mats to visualize story problems. When the story problem requires addition, they simply add the appropriate amount of counters to each part and add the two parts to find the whole sum. When the story problem requires subtraction, they start with the whole number in one of the parts, move the numbers that are being subtracted into the other part, and then count the number left in the first part. Using the part-part-whole mat in this way helps students see how addition and subtraction are related.