In every statehouse in the country, and in many countries overseas, you will see a statue of Lady Justice. She is usually blindfolded to show that she is impartial. In one hand, she holds a sword to show that justice will be enforced, and in the other, she holds a pair of scales. Why?

#### Why It Matters

Scales teach us how a very important mathematical concept, an equation, works. When the two sides of a scale have nothing in them—just as the one Justice is holding—they balance and hang level. To use a scale, you put the goods you want to weigh in one pan and then you gradually add weights to the other, until the scales balance. The total of the weights is the amount the goods weigh.

But what happens when you add another weight to the weighted side? The scale is no longer balanced and the pans are no longer level—that is, unless you add the same weight to the other side; then and only then will the scale return to being balanced.

The same principle applies in math. To keep an equation in balance, whatever you do to one side you must also do to the other. And that’s precisely how Justice maintains impartiality: by weighing both sides of the evidence equally and fairly.

See for yourself how to balance a scale: http://www.youtube.com/watch?v=pHXQXUvQ7yY

#### Explore More

Watch the video below to learn more about how scales are used to help solve equations.

http://www.youtube.com/watch?v=0S_pFYxyfhg