Hi, my name is Bassem Saad and I'm a Math Ph.D. candidate at U.C. Davis, and I'm here today for About.com to talk about ratios.A ratio is a mathematical way of comparing two different quantities, and we can write this in several different ways. If I wanted to relate seven and three, I have three ways of doing this: 7 to 3; 7:3; and 7/3. And just like a fraction, ratios can be simplified. For instance, if I had the ratio of 90:30, I would want to find the greatest common divisor (in this case 30) and divide it into each quantity, so that this ratio of 90:30 can be simplified down to 3:1.So let's take a look at some real-world examples. If you're at a restaurant where there are ten tables to every one server, you can pretty much guess it's going to be awhile before anyone comes around to take your order. Or say you were traveling at a ratio of 90 miles to every one hour – there's a good chance you're going to get a ticket. A percentage is a special ratio; it stands for parts of a whole or parts to 100. So, 20 percent is 20 parts to 100, or equivalently, 1:5.And those were the basics of ratios. Thanks for watching, and to learn more, visit us on the web at About.com.