Parts of Whole Things

People often confuse the terms ratio and proportion.A ratio is a relationship between two or more quantities. For example, the ratio of flour to sugar in a recipe may be 4:1 (4 cups flour to 1 cup sugar). The ratio of legs to ears to noses on a dog is 4:2:1.A proportion is a statement that two ratios or two fractions are equal. For example, the statement 8:6 = 4:3 is a proportion.Similarly, the statement 1/2 = 3/6is a proportion.The key to solving proportions is this: If a:b = c:d (or a/b = c/d), then ad = bc.

This picture shows a 3:1 ratio of blue paint to white paint.(Image hosted at http://www.bbc.co.uk/skillswise/numbers/wholenumbers/ratioandproportion/ratio/factsheet1.shtml)