A proportion is a statement of equality between two ratios. Since the ratio of 2 to 5 is the same as the ratio of 4 to 10, we can say that the two ratios are a proportion. The same proportion can be expressed as 2:5 = 4:10, 2 ÷ 5 = 4 ÷ 10, or 2/5 = 4/10. Notice that 2/5 = 0.4000 = 4/10.