A recipe for lemonade says to use 8 cups of water and 6 lemons. If 4 cups of water and 3 lemons are used, it will make half as much lemonade. Both recipes taste the same, because \(8:6\) and \(4:3\) are equivalent ratios.

The origin is the point \((0,0)\) in the coordinate plane. This is where the horizontal axis and the vertical axis cross. The origin is sometimes marked with the symbol \(\mathcal{O}\).