Hi, my name is Bassem Saad. I'm a Math Ph.D. candidate at U.C. Davis, and I'm here today for About.com to show you how to solve proportions with multiple variables.Remember, a proportion is an equation with a ratio on either side of the equal sign. And when you're trying to solve proportions with multiple variables, you really want to solve for just one variable and move everything else to the other side of the equal sign.Here we want to solve for y; that means we want to move everything over to the right side of the equation so we have y by itself on the left side. First thing we can do is multiply both sides of the equation by x to give us ten y equals five x over two. The next thing we want to do is divide both sides of the equation by ten. And here we just have two times ten, which is 20. And now we have y equals five x divided by 20. We can simplify this, since five goes into 20 four times, to give us our solution of y equals x over four.Proportions between two variables have been used by biologists as simple growth models for various organisms, and physicists have used these types of proportions to model radioactive decay. And now you can solve proportions with multiple variables too. Thanks for watching, and to learn more, visit us on the web at About.com.

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