The document explains ratios and provides examples of calculating different types of ratios from sets of numbers. It gives the ratios of circles to squares, circles to clouds, and other figures in a set of 15 numbers. It then provides word problems to calculate ratios such as girls to boys in a class of 30 students, the length and width of a rectangle, and the length and height of a dog. The document demonstrates how to write ratios in fraction form and calculates various part-to-part, part-to-whole, and whole-to-part ratios.