One way of finding the dollar up on a purchase using a number line. There are 12 pages with 6 themes - every two pages has a theme. On each page there are 5 questions. With my students, they find the first number in the price and circle it on the number line. They decide if there is change or not. If there is change they go one up on the number line, and if not they stay at the same spot on the number line.