Using ratios of sides is really helpful when working with similar shapes. Let’s break it down step by step:

1. Find Similar Shapes: First, check if the shapes are similar. This means that their angles are the same and the lengths of their sides follow a certain pattern.

2. Set Up Ratios: Look at the lengths of the matching sides. For example, if you have two triangles, $ABC$ and $DEF$, that are similar, you can compare side $AB$ to side $DE$. This ratio can help you figure out the lengths of any missing sides.

3. Solve for Missing Lengths: If you know some of the side lengths, you can set the ratios equal to one another. For instance, if you know that $AB/DE$ is equal to $AC/DF$, then you can find the length of a side that you don’t know yet.

Using this method makes solving geometry problems much simpler!