Final answer:
Figuring out the unit price of something is useful when shopping because it helps you determine the best deal.
Step-by-step explanation:
The unit price of something is useful when shopping because it helps you determine the best deal. By comparing the unit prices of different products, you can see which one offers the most value for your money. For example, if you're buying a snack, you can compare the prices of different sizes or brands to see which one gives you the most snack for the least amount of money.