Learn how to calculate percent as a rate per 100 in this video from KQED. In the accompanying classroom activity, students model percent with a 10 x 10 grid. After watching the video, they create a design or picture on a 10 x 10 grid, using a specified percentage of particular colors. They then consider the percentage of each color in the designs of the class as a whole. To get the most out of the lesson, students should be comfortable multiplying a whole number by a fraction with a denominator of 100.