The Bureau of Engraving & Printing prints all of America's money. Each year they make roughly nine billion bills that are then circulated around the world. But printing money is not a simple process. There are criminals who try to counterfeit money; make fake money. So the Bureau tries hard to ensure the real money is very hard to copy.

Sarah Church is a chemist for the Bureau. She worked on the project to create a new hundred-dollar bill. This new bill incorporates many security measures that make it difficult to counterfeit. Sarah helped design a special color-shifting ink which looks green when viewed from one angle and black when viewed from another. Math is crucial in the chemical composition of this ink. If the fractions are off, the color won't shift. "It's hard to even think of not using math," Sarah says. "Math is just so thoroughly spread throughout everything we do."